Management of patients with severe traumatic brain injury (sTBI) is highly variable and inconsistently aligned with evidence derived from high-quality trials, including those examining intravenous fluid resuscitation and use of decompressive craniectomy surgery. This study explored the barriers and facilitators of general and specific evidence-based practices in sTBI from the perspectives of stakeholder clinicians.This was a qualitative study of semistructured interviews conducted with specialist clinicians responsible for acute care of patients with sTBI. Interview analysis was guided by the Theoretical domains framework (TDF), and key themes were mapped to relevant TDF behavioral domains.Ten neurosurgeons, 12 intensive care specialists, and three trauma physicians from six high-income countries participated between May 2020 and May 2021. Key TDF domains were environmental context and resources, social influences, and beliefs about consequences. Evidence-aligned management of patients with sTBI is perceived to be facilitated by admission to academic research-oriented hospitals, development of local practice protocols, and interdisciplinary collaboration. Determinants of specific practices varied and included health policy change for fluid resuscitation and development of patient-centered goals for surgical decision-making.In choosing interventions for patients with sTBI, clinicians integrate local environmental, social, professional, and emotional influences with evidence and associated clinical practice guideline recommendations. This study highlights determinants of evidence-based practice that may inform implementation efforts and thereby improve outcomes for patients with sTBI.The online version contains supplementary material available at 10.1007/s12028-022-01551-x. Traumatic brain injury (TBI) is a global health problem: the worldwide annual incidence is 69 million, of which 5.48 million cases are severe TBI (sTBI) , 2. OutcA higher quality of clinical evidence has been associated with increased likelihood of implementation , 12. Of The determinants of evidence-adherent practice in acute sTBI, and of the above practice behaviors specifically, have not been explored from the perspective of treating clinicians. Such enquiry is important to identify factors that determine practice variability and is an essential precursor to developing active implementation strategies aimed at reducing evidence–practice gaps , 20. FurThis study aimed to identify factors that influence the adherence to evidence in the interdisciplinary acute management of patients with sTBI, with focus on choice of resuscitation fluids and decisions to perform surgery to treat intracranial hypertension, from the perspective of medical practitioners responsible for sTBI care.This was a qualitative study using in-depth semistructured interviews. Approval was obtained from the Monash University Human Research Ethics Committee (project number 23614). This report adheres to the Standards for Reporting Qualitative Research .The investigators were intensive care clinician researchers , with experience in the clinical management of TBI, and a knowledge translation researcher (PB). All investigators had research experience in international clinical studies in neurotrauma and critical care. Interview participants were hospital specialist clinicians responsible for the acute hospital care of patients with sTBI. During their stay in the ICU, clinical decisions regarding patients with sTBI are usually made by intensive care specialists and neurosurgeons, with input from trauma specialists. Therefore, clinicians from these disciplines were identified using purposive sampling from the professional networks of the investigators. Geography and academic affiliation may influence uptake of evidence; we aimed to recruit clinicians from Australian and international hospitals with comprehensive neurotrauma services.Consistent with a qualitative research paradigm, sample size was not predetermined. Sampling continued until no new qualitative themes emerged from three consecutive interviews .Participants received an invitation and explanatory statement by email and were asked if they were willing to participate in an interview lasting 30 to 45 min. Agreement to participate and acknowledgment of the explanatory statement implied consent. Single one-on-one interviews were conducted by the lead author (DG) via videoconference  with all but two participants, who requested in-person interviews. Interviews were recorded and transcribed verbatim using professional transcription services . Checked transcripts were imported into NVIVO 12  to manage data and facilitate analysis.Initial open interview questions explored clinicians’ perceptions of the general determinants of evidence-based practice in sTBI, with focused prompt questions to explore the contribution of CPGs and hospital protocols . Interview content then shifted to the two specific practices shown in randomized controlled trials to alter patient-centered outcomes: namely, fluid resuscitation and decompressive craniectomy for intracranial hypertension. Follow-up prompt questions explored the influence of key clinical trials pertaining to these interventions. The final area explored interdisciplinary dynamics and potential sources of bias between professional groups. The interview guide was developed by investigators with expertise in clinical content (DG and DJC) and qualitative and knowledge translation research (PB). Questions were piloted with two clinical staff, and the interview framework was updated.Consistent with previous published approaches , in thisUsing NVIVO®, one investigator (DG) performed open thematic coding and recoding of transcripts in an iterative back-and-forth process. Statements by different participants with similar or related underlying ideas (including statements expressing the opposite belief regarding influence of the same factor) were collected in thematic groups within relevant TDF domains. For example, statements regarding the influence on practice of hospital protocols would be grouped under a theme of ‘Local resources’ within the ‘Environmental context and resources’ domain (Supplementary Tables S1–S3). Emergent themes were subsequently tested for applicability, validity, and consistency. Themes coded to more than one domain were cross-indexed. After three interviews were coded, coding was reviewed with a second investigator (PB).A domain was considered salient if associated themes were identified consistently by participants or were deemed of high impact on clinical practice by researchers or participants, or if there was a combination of these features.Between April 2020 and May 2021, twenty-five medical specialists participated in semistructured interviews: ten neurosurgical specialists, 12 intensive care specialists, and three trauma specialists. Participants worked at eight different hospitals that receive and manage patients with sTBI in six high-income countries. All but one hospital had comprehensive neurosurgical services on-site. Participants were predominantly male (84%) and White (80%), of variable age (76% aged 36–55), and working in metropolitan areas (92%). Most were from Australia (76%), and half were from a single academic center (Table Each of the practice areas discussed had their own pattern of influencing factors (Supplementary Tables S1–S3). The following is a summary of findings. Illustrative quotations from the transcripts are shown in Table The key general factors thought to influence clinical practice in management of patients with sTBI were grouped within six theoretical domains (Supplementary Table S1).On the basis of reported experience and observations, participants from all disciplines stated that practice was more likely to be evidence aligned in academic university-affiliated hospitals than nonacademic hospitals. Hospital characteristics cited as facilitators included presence of subspecialized staff, established internal processes of interdisciplinary engagement and quality improvement and engagement with clinical trial networks.All clinicians perceived local institutional practice protocols to facilitate consistent evidence-based practice and in some cases, more so than widely disseminated CPGs, such as those produced by the BTF. Others cited the benefit of local protocols in providing pragmatic evidence-based guidance to nonspecialist bedside staff without requiring them to have in-depth knowledge of TBI literature.Clinicians of all disciplines noted that audit of practice to identify any evidence–practice gaps was an essential prerequisite to motivating improvement.Several clinicians felt strongly that local participation in clinical research was associated with implementation of evidence; they reasoned that the interventions tested at their institutions would be relevant to the local patient case-mix, championed by local investigators, and, therefore, readily adopted. Additionally, local research engagement reflects attention to contemporary evidence even beyond those interventions investigated in locally championed studies.Accreditation by specialist bodies and changes in government policy were highlighted as potent enablers of evidence-based practice. Participants in North America stated that linking accreditation of trauma hospitals with specific elements of the BTF guidelines had improved practice.Several intensive care clinicians noted that harmful medications and procedures may remain available despite recommendations against their use and that it should be relatively straightforward to make them less available.Social influences related to interprofessional relationships were highlighted by most participants as important determinants of practice. These were frequently cited in association with hospital and environmental characteristics.Many clinicians favorably cited collaborative, interdisciplinary activities  and management of critically ill patients with TBI as a potent enabler of evidence-aligned care, noting that different specialty groups brought different knowledge and skills. Several participants noted that such collaboration was dependent on a culture of positive, respectful engagement. Advocacy of key opinion leaders was also acknowledged as a driver of practice change and adoption of evidence.Multiple participants expressed nihilism about currently available treatments, stating that research has not improved outcomes for patients following TBI and that the best approach is to avoid causing additional harm with potentially dangerous or overly invasive interventions.Others cited anecdotes of satisfactory patient outcomes following non-evidence-aligned practice to justify such practice or highlight persistent knowledge gaps. Improvements in commonly used but short-term metrics, such as normalization of intracranial pressure or reduced length of stay in ICU, were also cited as possible perverse incentives for non-evidence-aligned therapies. To counter this, performance and audit metrics should align with patient-centered outcomes that include long-term functional recovery rather than short-term physiological markers or surrogate end points.Participants from all specialties opined that current practice, particularly neurosurgical practice, can be dogmatic and based on outdated evidence. Clinicians perceived themselves and others to be averse to change, particularly in situations in which new knowledge conflicted with established paradigms. Treatments were more likely to be adopted if they fitted an accepted model of TBI pathophysiology compared with treatments with mechanisms that were less understood but were nevertheless proven to change outcomes.The simplicity and ease of implementation of interventions tested in clinical trials was perceived to be associated with their rapid adoption, and vice versa. Clinicians noted that this could also be a barrier to evidence-based care, wherein ready availability of harmful treatments enables their inappropriate use. These observations overlapped with themes mapped to environmental context and resources.Neurosurgeons and ICU and trauma specialists perceived different but overlapping areas of responsibilities for patient care: neurosurgeons did not participate in early in-hospital resuscitation of patients, including fluid resuscitation, whereas ICU specialists perceived that intracranial procedures were exclusively the responsibility of neurosurgeons. All groups felt shared responsibility for overall quality of patient care.Several neurosurgeons and one ICU specialist observed that most neurosurgeons did not subspecialize in management of TBI, preferring to concentrate on other areas. However, neurosurgeons who delegated responsibility for patient management were perceived to be a potential barrier to evidence-aligned care.Nearly all participating clinicians reported and/or demonstrated knowledge of the pathophysiology of TBI sufficient to appreciate the rationale for different CPGs and usually referred, by name, to the BTF guidelines.However, these CPGs were not consistently held to be facilitators of optimal practice. Several clinicians perceived available CPGs to be inadequate to facilitate best practice, and many presented reasoned judgments for why they may be barriers to evidence-based practice.The underlying evidence was held to be insufficiently robust or poorly generalizable because of methodological concerns, therefore justifying alternative management. The variable pathophysiology and complexity of TBI was cited as an indication for personalized care on the basis of an individual patient’s characteristics rather than strict adherence to evidence-based guidelines. Some noted the delays between publication of the evidence and subsequent CPGs as a cause for persistent non-evidence-based practice. Finally, the BTF guidelines were held to be rigorously evidence focused at the expense of being nonpragmatic, for example, in not providing stepwise guidance on management of intracranial hypertension because of a lack of high-quality comparative data.Others held more favorable views on the CPGs as facilitators of evidence-based practice, citing their value in providing instructions for clinicians without in-depth knowledge of underlying science and clinical trial evidence. Additionally, guidelines were held to be a baseline standard against which actual practice could be audited and deviations interrogated.Following discussion of determinants of neurotrauma practice in general, interview questions focused on the two treatments shown to be potentially harmful: fluid resuscitation with albumin and surgical decompressive craniectomy.Key factors reported to influence the choice of intravenous resuscitation fluids following sTBI were grouped within the following theoretical domains (Supplementary Table S2).Restricting availability of potentially harmful fluids was seen as being the most effective mechanism of preventing their administration and rapidly improving practice. Such restriction was reported to have been achieved in some hospitals by charging a high price per unit and by a change to blood bank policies to require consent for administration of blood-derived products, including albumin. Reduced availability would reduce the risk of unknowing clinicians inadvertently prescribing albumin.With few exceptions, in response to open questions on determinants of intravenous fluid choice, participants of all disciplines cited the physiological impact of different intravenous fluid types rather than impacts on patient-centered end points of clinical trials, such as survival or functional recovery.Participants demonstrated or expressed awareness of evidence regarding the use of albumin that was in keeping with their scope of practice. In practice, neurosurgeons are not involved in fluid resuscitation of patients, and several acknowledged this was outside their knowledge base. Among ICU specialists, several worked in countries where albumin is not readily available, so they reasoned they had little motivation for exploring this evidence. However, some participants in countries where albumin is available were similarly unaware or noted that albumin was not used frequently but were uncertain why. There was greater awareness among intensive care clinicians with clinical research experience or academic appointments.Key factors thought to influence the practice of using decompressive craniectomy to reduce intracranial pressure were grouped within the following theoretical domains (Supplementary Table S3).Participants’ responses regarding decompressive craniectomy were commonly informed by synthesizing the results of key trials. Clinicians commonly inferred that decompressive craniectomy is an intervention of last resort, only considered after the full range of nonsurgical therapies have failed. Participants held that decompressive craniectomy improves intracranial pressure while acknowledging that it may also increase the number of severely disabled survivors. For this reason, it was felt that use of decompressive craniectomy should be reserved for those with the best chance of neurological rehabilitation: generally younger people and those without preceding functional impairments. Some clinicians emphasized reduction of intracranial pressure (a widely accepted surrogate marker of brain injury and treatment target) as the reason to perform decompressive craniectomy, irrespective of high-quality evidence showing harm.Cultural context was noted to be an important factor in deciding whether to perform life-sustaining surgeries with the expectation that the patient may survive with debilitating disability. Clinicians noted that within some ethnic or religious communities, human life is considered sacred in any condition, meaning there is a default to active intervention even in situations in which clinicians might consider the prognosis unfavorable.Despite being cognizant of the risk of poor outcomes, participants from all disciplines (particularly neurosurgeons) reported emotional pressure to perform decompressive craniectomy surgery when presented with a patient with refractory intracranial hypertension. This pressure was both external (from families or other clinicians) and internal (a human bias toward active intervention).With few exceptions, discussions with relatives or friends of the patient to determine their values were reported to be essential in deciding therapies. If a family expressed the view that a patient would not wish to survive with severe disability, this may prompt clinicians to advocate for less invasive  therapies. Some clinicians noted that families may struggle to incorporate the complexity and uncertainty of management and may advocate for decompressive craniectomy to be performed in the belief that the more invasive therapy is more likely to result in improved outcome.Given the complexity of decision-making, clinicians from all groups reiterated that collaborative interdisciplinary discussions at a senior level were essential to decide the most appropriate management for individual patients. Although decompressive craniectomy can only be performed by neurosurgeons, both they and ICU specialists perceived that they share responsibility for decisions regarding surgery. In some regions this has shifted over time such that greater responsibility now rests with the ICU. One academic neurosurgeon noted favorably that few patients have refractory intracranial hypertension if nonoperative therapies are used appropriately; therefore, decompressive craniectomy is rarely indicated and the evidence is rarely applicable.In this qualitative exploration of stakeholder clinicians’ perceptions of the acute management of sTBI, we found that in determining practice, evidence-based recommendations are integrated with local environmental, social, professional, and emotional influences. Our study builds on previous findings that adherence of neurocritical care practice to evidence is a function of factors related to institutions, clinicians, and the guidelines themselves , 25, 26.The health care environment is a potent facilitator of evidence-based sTBI practice in general through different mechanisms at different levels  depending on the practice behavior. Among the sampled clinicians, organizational culture promoting interdisciplinary academic activities  and presence of key opinion leaders were consistently cited as facilitators of evidence-based practice, and interdisciplinary conflict arising from inadequate collaboration was seen to be a barrier. These findings are consistent with previous studies of clinicians’ perceptions of enablers of guideline-based acute hospital care in neurotrauma and antenatal settings , 27 and Evidence-based fluid resuscitation practice in TBI can be achieved with changes to the policy environment. Restricting availability of albumin is relatively uncomplicated given that safer alternatives exist with fewer barriers to administration. Fluid resuscitation practice in critically ill patients has changed in response to evidence , but in Enabling evidence-aligned use of decompressive craniectomy is more complex, with influential factors intersecting multiple TDF domains. A decision whether to offer decompressive craniectomy is usually made at a time of emotional stress for families and clinicians, when nonoperative treatment has failed to treat intracranial hypertension and patients are at immediate risk of dying. Few participants explicitly prioritized high-quality clinical evidence comparing patient-centered end points over lower-quality evidence. Although participants demonstrated knowledge within expectations for their specialty groups, at times their awareness of established models of TBI pathophysiology and the likely physiological impacts of specific therapies overrode or appeared to compete with adherence to evidence-based CPG recommendations. Consistent with previous findings, this was particularly true if the mechanisms of the recommended intervention were inconsistent with the clinician’s existing knowledge . CliniciPrevious studies suggest that adherence to CPGs is enhanced when clinicians have confidence that the recommendation will produce the desired outcome . Nearly This study has several notable strengths, including sampling of clinicians from multiple specialties involved in the care of patients with sTBI, interviews conducted by a content expert, and analysis of influential factors using a validated theoretical framework by content experts and an experienced knowledge translation researcher. Our study is unique in exploring the interdisciplinary dynamics associated with acute management of sTBI and in examining determinants of two specific practices. Our study also has some limitations. We used the TDF predominantly in the analysis of responses rather than in the development of the interview guide; assignment of responses to TDF domains was post hoc, but this approach allowed for analysis according to dominant, unprompted themes. The clinicians were predominantly sampled from a single Australian academic neurotrauma center, with potential for unconscious or confirmation bias to influence perspectives. Although participants ranged in age and breadth of experience, the factors they identified are relevant to the circumstances in which they were sampled and may not be relevant with changes in practice, environment, and evidence. These issues, as well as the limited racial and gender diversity of respondents, potentially limit the generalizability of our results.In a sample of predominantly Australia-based specialist clinicians, factors influencing management decisions and the implementation of key evidence-based practice recommendations for sTBI were identified. Academic organizational culture, resources, and interdisciplinary collaboration were determinants that facilitated evidence-based practice. Fluid resuscitation practice could potentially be improved with health policy changes, whereas an explicit focus on patient-centered treatment goals could direct optimal surgical practice. This study highlights determinants of evidence-based practice that may inform tailored implementation efforts in similar settings and thereby improve outcomes for patients with sTBI.Supplementary file 1. Interview guide for clinicians involved in acute management of severe traumatic brain injury.Supplementary file 2. Table S1. Factors perceived generally to influence practice in severe traumatic brain injury; Table S2. Factors perceived to influence practice in fluid resuscitation of patients with severe traumatic brain injury; Table S3. Factors perceived to influence practice of surgical decompressive craniectomy in patients with severe traumatic brain injury.Below is the link to the electronic supplementary material.


Triage errors are a major concern in health care due to resulting harmful delays in treatments or inappropriate allocation of resources. With the increasing popularity of digital symptom checkers in pre–primary care settings, and amid claims that artificial intelligence outperforms doctors, the accuracy of triage by digital symptom checkers is ever more scrutinized. This paper examines the context and challenges of triage in primary care, pre–primary care, and emergency care, as well as reviews existing evidence on the prevalence of triage errors in all three settings. Implications for development, research, and practice are highlighted, and recommendations are made on how digital symptom checkers should be best positioned. Across health care settings globally, the inability of supply  to meet demand  means significant limitations exist on access to medical assessments and treatments. Safe, effective, and fair distribution of health care resources therefore requires some form of filtering and direction, or triage, of individuals within health care services based on type or severity of symptoms and/or initial likely diagnoses.Emerging health technologies have the potential to provide answers to this problem, in supporting the initial assessment of individuals presenting with symptoms to ensure that they access the right area of the health system with the appropriate degree of urgency. Digital symptom checkers represent one approach, providing users with triage recommendations based on their presenting symptoms and responses to screening questions. However, the extent to which digital symptom checkers can safely be used alongside or in place of existing forms of initial medical assessment is currently unclear, with the potential significance of error in triage recommendation being substantial.In this article, we discuss existing evidence on triage errors in pre–primary care , in comparison with primary care and emergency care, and provide recommendations on how digital symptom checkers might be best positioned to support users and existing health systems.The Oxford English Dictionary defines triage as “the assignment of degrees of urgency of need in order to decide the order of treatment of a large number of injured or ill patients.” The sorting of patients into emergency, urgent, nonurgent, and self-care categories becomes essential in all health care settings where there is a need to manage allocation of limited health care resources .Triage errors can be described as either undertriage or overtriage. Undertriage occurs when the level of urgency of an individual’s condition is underestimated  and theyTriage is likely to take place at many stages of a patient’s symptomatic and diagnostic journey, from initial awareness of symptoms through to final established diagnosis and definitive management or resolution of symptoms. Experiencing symptoms is common and frequently does not require medical assessment or treatment . Most inIt has been suggested that the “pre–primary care” health sector, where individuals have reached the stage of considering seeking formal advice on their symptoms but have not yet seen a physician, should be the target of new technological approaches to triage . BuildinDigital forms of consultation and triage lack any opportunity for physical examination or for other human interaction, where subtle cues may be picked up. Fully digital consultation systems often lack access to users’ medical histories and are entirely dependent on the data entered by users at the time of consultation. These limitations mean that errors are inevitable. Although face-to-face consultation is often viewed as the gold standard of primary care, it is not free from limitations. These might arise from biases and cultural differences between the clinicians and the patients  ,10. To cStudies that investigate triage errors in primary care are scarce. A systematic review assessing the safety of telephone triage in out-of-hours care compared with standard face-to-face doctor assessment suggested that triage was safe in 97% (95% CI 96.5%-97.4%) of all patients contacting out-of-hours care and in 89% (95% CI 86.7%-90.2%) of patients with high urgency . This reAlthough some primary care telephone triage is done by doctors, much is done by nurses, sometimes using computer-based clinical decision support systems . A studyIn emergency department settings, triage error rates appear to be markedly higher. Tam et al  found thThe accuracy of digital symptom checkers in providing triage has been met with skepticism. There is limited evidence in this area, but vignette studies have suggested that triage error rates have been shown to be high for digital symptom checkers ,24. One Triage advice provided by symptom checkers is found to be more risk averse than that provided by health care professionals ,32, withAlthough most studies regarding the accuracy of symptom checkers were carried out through clinical vignettes ,24, someEvidence of triage error rates in primary care, in emergency care, and by symptom checkers is summarized in Triage error rates in primary and emergency care vary widely across the literature , and difIt is worth noting that this article is not a formal systematic review, thus no specific strategies or selection criteria were applied to our literature search. This might result in potentially relevant studies being missed, despite our best effort to ensure appropriate studies regarding triage accuracy were included. However, from our consideration of the literature, we observed a high level of heterogeneity among the rates of triage errors across studies. The heterogeneity of triage error rates in primary care, pre–primary care, and emergency care is attributable to a number of factors. Most importantly, case mix and approach to/purpose of triage differ substantially across these settings. The number and type of conditions considered in each study also differed. Although the majority of studies included a mix of acute and chronic conditions, some only considered one type of disease . Studies that assessed triage accuracy in more conditions were more likely to report higher error rates. In addition, the methods used to identify triage errors were heterogeneous. Eight methods were commonly employed in assessing triage accuracy, namely autopsies, patient and provider surveys, standardized patients, second reviews, diagnostic testing audit, malpractice claims, case reviews, and voluntary reports . StudiesConsideration of triage error in primary care is particularly timely in the current unprecedented public health context. The recent COVID-19 pandemic has challenged the ability of health systems worldwide to meet demand, with services in some countries completely overwhelmed. A pressing need to avoid all but the most urgent and essential health service use, and to limit face-to-face interaction between health care professionals and members of the public to an absolute minimum, has led to the adoption of a “remote total triage” system in primary care using telephone and online consulting in many countries .Whether the digital symptom checkers’ level of performance for triage is acceptable depends on the purposes for which they are used . If sympAlthough seeking to avoid unnecessary burden on health services, the lack of available background information and inability to include information from physical examinations or nonverbal cues means that any remote assessment system will likely need to take a risk averse approach to triage. Thus, it is arguably appropriate that digital triage tools adopt this approach.Most studies assessing the triage error rates among symptom checkers are conducted through clinical vignettes. The preparation and evaluation of vignettes need to be standardized to allow for external validity and comparability. Furthermore, clinical trials where symptom checkers’ rates of triage error are compared with those of face-to-face consultation should be encouraged. This method not only enables the assessment of triage accuracy but also allows the examination of users’ compliance with triage advice and possible benefits for the health care system.There is little evidence on users’ compliance with triage advice, in either traditional forms of triage or that given by digital symptom checkers, nor is there data on consequences of symptom checker errors. Additionally, little is currently known about patient expectations and health beliefs in relation to digital diagnostic and triage tools. It seems likely that most individuals would place lower weighting on the advice of a symptom checker than a human clinician, and use the information provided by these tools as part of their decision-making process. However, in times of increasing reliance on digital technology, it is possible that some individuals may have greater trust in these tools than might be expected. Research is clearly needed to clarify these questions, but developers should assume a relatively high degree of reliance of users on the recommendations that symptom checkers provide.In addition, well-conducted research to understand the clinical effectiveness of digital symptom checkers in effectively triaging individuals  is urgently needed. To inform decisions of users and policy makers adequately, this must incorporate formal comparison with existing provision, with a focus on primary care telephone and online triage.Digital symptom checkers should largely position themselves in the pre–primary care triage/self-care area—evidence does not currently support the ability of artificial intelligence to provide effective consultations at the level of those that would normally take place in traditional face-to-face primary care or emergency department setting.Digital symptom checkers can be appropriately promoted as a safer alternative/effective addition to existing sources of information (such as self-directed online searches) for individuals prior to seeking formal health advice.Providers of digital symptom checkers should seek to ensure that triage error rates fall within the lower thresholds demonstrated in existing evidence of those in primary care telephone triage .Developers of symptom checkers should make efforts to expand the evidence base in this area, including establishing systems to gain user feedback on triage accuracy/appropriateness, as well as engaging with academic partners to carry out formal research. Findings in terms of limitations and error rates should be clearly publicized and highlighted to users.Current methods employed to study symptom checkers’ triage accuracy such as case vignette studies should be standardized to allow for external validity and comparability. Clinical trials where key outcome measures include the accuracy of both outcome conditions and triage should also be conducted. A clear distinction between over- and undertriage should be made to provide data for safety monitoring and economic evaluation.There is very limited evidence and no clear gold standard comparison for triage errors in digital symptom checkers, meaning that it is not possible to make recommendations on an acceptable error rate. Positioning symptom checkers in the self-care/pre–primary care triage setting therefore seems to be most appropriate and where they can likely add value for individuals experiencing symptoms. Industry and academics should work together to develop the necessary evidence, and efforts should be made to collect user feedback and outcomes data. Until clearer comparisons with existing care are available, digital symptom checkers and triage tools should appropriately continue to take a risk averse approach in the recommendations they give to users.


Many inborn errors of metabolism and genetic disorders affect the brain. The brain biochemistry may differ from that in the periphery and is not accessible by simple blood and urine sampling. Therefore, neuroimaging has proven to be a valuable tool to not only evaluate the brain structure, but also biochemistry, blood flow and function. Neuroimaging in patients with inborn errors of metabolism can include additional sequences in addition to T1 and T2-weighted imaging because in early stages, there may be no significant findings on the routine sequnces due to the lack of sensitivity or the evolution of abnormalities lags behind the ability of the imaging to detect it. In addition, findings on T1 and T2-weighted imaging of several inborn errors of metabolism may be non-specific and be seen in other non-genetic conditions. Therefore, additional neuroimaging modalities that have been employed including diffusion tensor imaging (DTI), magnetic resonance spectroscopy, functional MRI (fMRI), functional near infrared spectroscopy (fNIRS), or positron emission tomography (PET) imaging may further inform underlying changes in myelination, biochemistry, and functional connectivity. The use of Magnetic Resonance Spectroscopy in certain disorders may add a level of specificity depending upon the metabolite levels that are abnormal, as well as provide information about the process of brain injury . It is even more challenging to understand how genetic or metabolic disorders contribute to short and/or long term changes in cognition which represent the downstream effects of IEMs. In order to image “cognition” or the downstream effects of a metabolic disorder on domains of brain function, more advanced techniques are required to analyze underlying fiber tracts or alternatively, methods such as fMRI enable generation of brain activation maps after both task based and resting state conditions. DTI can be used to look at changes in white matter tracks. Each imaging modality can explore an important aspect of the anatomy, physiology or biochemisty of the central nervous system. Their properties, pros and cons are discussed in this article. These imaging modalities will be discussed in the context of several inborn errors of metabolism including Galactosemia, Phenylketonruia, Maple syrup urine disease, Methylmalonic acidemia, Niemann-Pick Disease, type C1, Krabbe Disease, Ornithine transcarbamylase deficiency, Sjogren Larsson syndrome, Pelizeaus-Merzbacher disease, Pyruvate dehydrogenase deficiency, Nonketotic Hyperglycinemia and Fabry disease. Space constraints do not allow mention of all the disorders in which one of these modalities has been investigated, or where it would add value to diagnosis or disease progression. Research from preclinical models is delving into the etiologies of how a metabolite intoxication accounts for the specific cognitive and neurologic findings observed in IEM patients related to the time of injury or many years later,7. IEM-associated brain injury patterns may be region specific and primarily cause gray matter or white matter damage, but typically is more complicated and may include damage to neurons and the supporting glia at the same time or later in the course. In children, this occurs on the backdrop of development of some of the very systems that are impacted later, such as executive function.Many inborn errors of metabolism (IEMs) are associated with an acute onset of progressive symptoms and irreversible brain injury, putamen in certain mitochondrial cytopathies, or the globus pallidus in methylmalonic acidemia. There may be damage to regions that share a particular neurotransmitter system. This remains poorly understood and often requires preclinical investigations.It is not clear why a global insult such as IEM may cause more selective damage to particular sets of cells. This could involve deep gray matter neurons, white matter, the putamen  as seen in glutaric aciduria type 1Neuroimaging has already shown great potential for the investigation and management of IEM and other genetic conditions. Given its non invasive nature, it allows for longitudinal assessments and follow-up. Each modality may contribute something unique about the timing or pathology, and can be used as a biomarker to study the disease course or therapeutic intervention. One criticism has been that the findings on routine T1 and T2-weighted imaging are nonspecific and may not allow differentiation between disorders. In those cases, additional magnetic resonance images (MRI) sequences and/or modalities enables a higher diagnostic specificity. Beyond establishing a diagnosis, MRI may be used to understand pathology, disease progression and long term impact of the disease on higher cognitive function with the use of functional MRI (fMRI) and functional near infrared spectroscopy (fNIRS). The latter techniques are important as therapy may lead to a decrease in a blood metabolite, yet there may be an elevation of a toxic compound in the CNS and the impact of damage on cognition and function may not be fully understood. These advanced modalities are not available in every hospital. However, the purpose of this review is not to mandate use of certain imaging modalities, but rather to highlight when certain imaging sequences may be useful to further understand the pathogenesis of a metabolic disorder. In addition, due to space constraints, it will not be possible to list every condition and its imaging characteristics. Rather, specific disorders will be highlighted in which recent literature has suggested the value of MRI in these conditions. Lastly, research into practice will use examples as to how multimodal imaging is applied in the clinical setting, leading to improved clinical management.. Another modality that can also give information about neural networks is fNRIs which is a less invasive and portable imaging modality (described below).The term “neuroimaging” describes sequences beyond T1 and T2 weighted imaging. Most clinical routine images at major medical centers include a fluid attenuation inversion recovery (FLAIR). Some centers are able to reformat a high resolution T1 weighted image and perform volume analysis using voxel-based morphometry (VBM) to measure differences in gray and white matter volumes. To understand the cognitive outcomes of IEMs, one can use fMRI to study the neural networks that underlie cognitive pathwaysMRI works by exploiting differences in water proton spins between tissue types  after the tissue is exposed to a radiofrequency pulse in a strong magnetic field. The subject’s head is enclosed in a head coil, and there is a body coil at the bed of the scanner. The coil serves as an antenna, converting electromagnetic waves into an electrical current, which is used to reconstruct the three dimensional images.Despite its utility as both a research and clinical tool, routine MRI detection is limited to macroscopic alterations in brain structure. It lacks the spatial resolution to provide information regarding microstructural neuropathology, and does not capture dynamic processes in space and time related to brain function and metabolism. Additionally, many macrostructural neuropathological phenotypes lag behind the presentation of associated clinical manifestations until there is critical amount of macroscopic damage that can be seen on an image.The advantages of MRI over CT include the lack of ionizing radiation, the ability to image in three orthogonal planes and the ability to better visualize the brainstem and cerebellum which are difficult to see in CT due to beam hardening artefacts. MRI is superior to CT in the evaluation of white matter pathologies. This is at the expense of longer imaging sequence times, need for sedation in children and sometimes lack of accessibility in an emergency situation.. As a result, maps of white matter fibers can be generated. Since water diffusion in cells corresponds to cell geometry in axons, diffusion MRI can also be used to make inferences about white matter architecture. One standard measure is anisotropy which refers to the property of being directionally dependent. Three measures of diffusion in tissue can be quantitated using DTI: magnitude (ADC), orientation of diffusion, and degree of anisotropy . The more unrestricted the water molecules are in their movement, the higher the ADC and the lower the anisotropy. DTI has in some cases shown to have predictive ability for example, in recovery from a traumatic brain injury.DTI is an imaging technique in which contrast is based on differences in the diffusion of water molecules. There is a rich literature that has focused on alterations in executive function, for example on large cohorts of children and adults with attention deficit disorders, Alzheimer disease, autism and post traumatic brain injury to name a few. Only recently has this been a topic of interest in inborn errors of metabolism.Understanding white matter integrity is important because underlying changes in neural networks are often aberrant white matter tracks. There are many well defined neural networks that play a role in cognitive functions such as working memory, attention and cognitive flexibilityet al. used a cognitive function battery demonstrating low scores for verbal and performance IQ, as well as low scores for memory and executive function. Subsequently, using diffusion tensor imaging, others found that compared to age- and gender-matched controls, patients with galactosemia had reduced volume in the left cerebellar white matter, the bilateral putamen, and left superior temporal sulcus. There was also lower fractional anisotropy and higher radial diffusivity values in the dorsal and ventral language networks compared to the controls.Doyle –25. Gross WM abnormalities seen at autopsy and on T1 and T2-weighted magnetic resonance images (MRI) have been reported in patients with PKU–36 and white matter (WM) changes are evident by the second decade of life.Phenylketonuria (PKU) is perhaps the best studied metabolic condition in terms of MRI imaging. The underlying neurobiological aspects of PKU include deficits in executive dysfunction. While not completely understood, it is believe to be related to the often seen myelination abnormalities. DTI studies have identified restricted diffusivity in individuals with PKU across a number of brain regions, including the centrum semiovale, posterior-parietal occipital cortex, prefrontal cortex, optic radiation, putamen, and anterior corpus callosum,37. WM alteration was indeed influenced by life-long metabolic control but the severity score of WM alterations did not correlate with IQ or Executive function scoring,36.Subtle executive function deficits especially in inhibitory control have been reported in patients with phenylketonuria (PKU), and this is seen despite early dietary restrictions,38. Two types of brain edema have been described in MSUD. Intramyelinic edema affects the myelinated white matter , thalami, and globus pallidi. Intramyelinic edema or “MSUD edema” is the more recognizable pattern, described as hyperintense on T2-weighted images, diffusion weighted imaging (DWI) and hypointense on T1-weighted images. DTI shows alterations in both ADC and fractional anisotropy (FA) values–42. Intramyelinic edema which is believed to be a consequence of energy failure leads to the accumulation of water molecules that intercalate between the myelinic lamellae resulting in the splitting of the myelin layers. This can be detected by DTI ,42. The end result of this process may be delayed myelination and white matter atrophy with the aforementioned cognitive sequelae.Maple syrup urine disease (MSUD) is a disorder involving the catabolism of branched-chain amino acids  and is caused by deficiency of the branched-chain ketoacid dehydrogenase enzyme. This suggests that, in addition to restricted water diffusion in the globus pallidus, MMA is associated with more widespread disturbances in white matter integrity. This is an example of how DTI proved superior to routine imaging in identifying these diffuse lesions. Neurocognitive lesions in MMA have yet to be investigated with fMRI.DWI has been used to investigate ADC in methylmalonic acidemia (MMA). It has been reported to be associated with restricted water diffusion in the globus pallidus that may resolve after clinical interventions including carnitine supplementation. Findings from 12 MMA patients demonstrated significant reductions in FA in the globus pallidus, frontal, temporal and occipital white matter using DTI and we’re not appreciated on conventional T1/T2 images.Niemann-Pick disease, type C1 (NPC1), is a rapidly progressive neurodegenerative disorder characterized by cholesterol sequestration within late endosomes and lysosomes. There are no specific or reliable imaging markers that can be used for management and prognostication. Cerebellar volume deficits are found to correlate with disease severity. Diffusion tensor imaging (DTI) of the corpus callosum and brainstem, has demonstrated abnormalities with microstructural disorganization that has shown some association with the degree of NPC1 severity.Studies using DTI have shown that radial diffusivity and fractional anisotropy are sensitive in vivo as biomarkers of white matter microstructural damage in this condition. Using DTI, early white matter injury has been detected in asymptomatic neonates with Krabbe. The DTI metrics have shown to correlate with motor and cognitive functions after hematopoietic stem cell transplantation (HSCT), and as a marker of white matter developmentet al. used DTI to study adults with OTCD. In all cases, DTI proved more sensitive than T2-weighted imaging for detecting abnormalities in normal-appearing white matter. The extent of abnormality in white matter in turn correlated with cognitive deficits. The location of the deficits in the frontal white matter correlated with pathways that subserve executive function, attention, and working memory which are impaired in this patient population.MR imaging in patients with ornithine transcarbamylase deficiency (OTCD) is often normal in late-onset disease, heterozygotes, or in those not in hyperammonemic crisis. Gropman .Given that the goal of therapy in IEMs is to decrease morbidity to the brain and other organs, understanding the impact of these disorders on brain injury and remodeling can help frame treatment and monitoring in patients. Differential neural networks underlying a cognitive process may arise due to injury to the native pathway, and/or development of an accessory pathway over time. Since T1 and T2 weighted changes in white matter tracts are only sensitive to significant, macroscopic damage, quantitative, early microscopic features of myelination and axonal integrity can be gleaned by using DWI and DTI which are used to study microstructural variance in white matter fiber tracts. It is popular in IEMs for monitoring of disease progression and therapeutic response.Magnetic resonance spectroscopy (MRS) is an imaging technique used to measure brain metabolism. MRS is performed with the same hardware used for anatomical imaging. Instead of an image, a spectrum is produced. The area under the peaks is proportionall to the concentration of the relevant metabolite. MRS studies of humans and genetically altered animals are feasible as are studies of cultured cells, histological tissue samples, and chemical extracts of tissues. A benefit of MRS is the lack of ionizing radiation. Therefore repeated scanning of patients including infants and children is feasible and acceptable. However, MRS is very sensitive to movement and the peaks can become wide and uninterpretable which makes it a difficult imaging modality to perform in unsedated children.MRS is noninvasive. Its use allows one to gain information relevant to tissue biochemistry and metabolismMRS allows measurement of chemicals in the brain. It is based on the principles of nuclear magnetic resonance. Magnetic resonance reveals the interaction between a molecule and an external magnetic field.1H, 31P, 13C, 7Li, and 19F. Those most studied include hydrogen (1H)  and phosphorus (31P). (13C) imaging is cumbersome but can be useful to study flux through the citric acid cycle which is relevant for many of the inborn errors of metabolism.The nuclei most relevant to complex human conditions are In order for MRS to effectively measure the key metabolites, the molecules must be relatively mobile within the tissue. Large macromolecules  do not show enough free movement and cannot be detectedd. There must also be a large enough concentration of atomic nuclei of a specific type to generate a recognizable signal/noise ratio in the millimolar range concentration.. The most common chemicals studied are N-acetyl-L-aspartate (NAA), total creatine (tCr) which is a sum of creatine (Cr) and phosphocreatine (PCr), choline (Cho), myo-inositol (mI), lactate (Lac), glutamate (Glu), and glutamine (Gln), known on low field MRI as “Glx”. In addition, amino acids, lipid, and gamma-aminobutyric acid (GABA) may be detected; but require editing. The number of metabolites seen will depend upon the chosen echo time (TE) and field strength with more metabolites seen on short TE. Long TE MRS is sufficient to evaluate lactate (if present), NAA, creatine, and choline Glu. Gln and mI are not detectable at long TE due to short relaxation times. These common chemicals can provide information about disease states: NAA: mitochondrial oxidative metabolism and marker for neuronal viability. It is also the source of acetyl groups for lipid synthesis; Cr and phosphocreatine (PCr): markers of creatine to phosphocreatine energy conversion; Cho: precursor for the neurotransmitter acetylcholine and membrane phospholipids, phosphatidylcholine, and sphingomyelin; mI: neuronal signaling molecule of the phosphoinositide pathway and osmoregulation; Lac: marker of anaerobic metabolism and Glu and Gln: neurotransmitters in the CNS. A number of MRS studies have been conducted in IEMs and are shown in the table .How does research neuroimaging impact on clinical practice? Our research in the UCDC has already allowed research into practice. As we have shown, Urea cycle-related disorders may show variable neuroimaging manifestations, ranging from normal to abnormal with or without a signature appearance. In the past, we have described the role of multimodal imaging in identifying biomarkers of neuronal injury in UCD patients. The diagnosis by clinical features and MRS was much faster than pending (in this case would have been next day) plasma amino acids and urine organic acids results. This research was put into clinical contact recently when we were able to achieve a rapid diagnosis and treatment of a 3 year old boy with mental status changes suspected due to new onset OTCD due to a high index of suspicion and classic findings on MR spectroscopy . This caet al. used Quantitative MRS to evaluate concentrations of brain metabolites in children with neonatal onset propionic acidemia. They tracked metabolic stability, during an acute encephalopathic episode prior to and after liver transplantation. They concluded that MRS was useful in this setting and believed it could also be used to evaluate potential therapies [Davison herapies ..In the last decade, advances in neuroimaging technologies have led to multiple studies investigating the neural networks of executive function (EF). EF has long been associated with the PFC involving working memory, inhibitory control and set shifting. Diamond speculated that neuroimaging can allow the investigation of many unanswered questions regarding cognitive functions and stated that fMRI and fNIRS could be of interest in studying the neural correlates of cognition. There are ample opportunities to employ this strategy in IEMsMRI imaging beyond routine structural imaging can shed light on processes that impact the brain during metabolic crisis. Collaboration with physicists and neuroimaging specialists can allow further detailed study and identify biomarkers that can be quickly put into clinical practice.


Nature, Alex Cagan, Adrian Baez-Ortega and colleagues found that many mammalian species present a similar somatic mutational load at the end of life. The mutational burden is independent of lifetime and body mass, only varying by a relatively small fold change among species.1 These data may suggest that mutational burden predicts mortality.In a recent study published in 2 While somatic mutations in recurrent cancer-driver genes clearly promote carcinogenesis, studying the influence of somatic mutations and tissue mosaicism for aging and age-associated diseases remained challenging, due to the enormous heterogeneity of small mutated clones. With the recent advancement in DNA sequencing technologies, long-standing questions regarding the evolution of somatic mutations can now be addressed.Already 70 years ago researchers hypothesized that cancer and aging were caused by an accumulation of mutations in somatic cells.3It was the epidemiologist Richard Peto who found an incongruity between logic and biological reality, known as Peto’s paradox. He noted that if somatic mutations develop at a linear rate, and mutations predict cancer, then large animals which have more cells and hence could acquire more mutations, should die sooner than smaller animals. However, this is not the case.1 The authors compared whole-genome sequencing analyses from micro-dissected single colon crypts of 16 mammalian species. The tissue is appropriate to study naturally occurring somatic mutation rates, given its conserved anatomical status and clonal origin. Indeed, the authors verified that mutation accumulation is linearly increasing over time within a species, as previously demonstrated in humans.4 However, the relative mutation rate is species-dependent and highly variable among species. Mutations presented in three consistent COSMIC mutation signatures across species . Importantly, the authors demonstrated that the somatic mutation rate is inversely proportional to lifespan in 16 mammalian species  is controlling this phenomenon. Thus, total mutational load better correlates with lifespan than individual mutational processes.5 Alternatively, a certain mutation burden may be tolerated without empirically detected physiological impacts on negative selective pressure, and perhaps mutation rate evolved alongside lifespan. Animals with shorter lifetimes can tolerate higher mutation rates, so less emphasis on extensive repair mechanisms may be paid for keeping the mutation rate low.Still puzzling are the causes of cellular and organismal aging. This study demonstrates a similar mutational burden at the end of life for mammals. Are the acquired mutations responsible for aging and dysfunction in cells, organs, and the whole organism? Then the mutation rate would be the pacemaker of the clock of life, and therefore a mutation threshold would limit lifespan. However, observations of individuals with inherited disabilities in certain DNA repair mechanisms resulting in a much higher somatic mutation rate do not show overt signs of premature aging.We still know little about the potential of acquired somatic mutations to cause (rather than associate with) age-related diseases other than cancer. While a direct consequence of the accumulation of mutations on cell function and survival in terms of aging processes appears rather unlikely, the cellular interplay involved in the body’s response to impaired organ performance may be influenced. Immune cell dysfunction caused by the somatic mutations in blood cancer-related genes in blood stem cells, known as clonal hematopoiesis, has gained medical interest. While these mutations provide a competitive advantage in the stem/progenitor cell compartment, they also cause detrimental functional changes in immune cells that have negative effects on the progression of cardiovascular diseases and thereby impact human aging in an organismal interplay. Aging is a multifactorial and complex process and is not solely dominated by the accumulation of somatic mutations in individual cells. Rates of telomere shortening, protein aggregation, and epigenetic alterations may equally predict mortality. Somatic mutations in certain cell types in multicellular organisms may impact on the stability of the network and cause unpredictable and disruptive forces on the organism.Many follow-up questions come to light when considering the study by Cagan et al. What are the molecular processes that determine and control mutation rates in divergent species? What are the selective pressures driving longer lifespans? Does the accumulation of somatic mutations in all tissues follow the same trends for a given species? This manuscript supports the discussions as to whether the mouse is a suitable model organism. For the data in this investigation, mice fit the model of aging and disease very well, however, the control of DNA integrity might differ between humans and mice.The study by Cagan et al. is a milestone study that can provide a new framework for how to view not only human health and disease, but mammalian life as a whole.


Immune genes of the vertebrate MHC vary among individuals. Each individual collection is optimally diverse to provide resistance against some infectious diseases but not too diverse to cause autoimmune diseases. MHC-dependent mate choice aims for optimally complementary MHC alleles. Each potential partner signals through body odor his/her MHC alleles. Identifying the signal molecules was a long-lasting puzzle solved only recently after many deviations as described. Commensal microbiota which are controlled by the individual MHC genes differ among individuals. They were suspected repeatedly to provide the signal, though mice raised germ-free could still smell MHC genes. Carrier hypotheses came in various versions, centered around the specificity of each MHC molecule for binding peptides from diseases, shown to T lymphocytes to induce the immune response. Volatiles of various origins were suggested to fill the place of the peptide and thus reflect the identity of the MHC molecule. Finally, the bound peptides themselves were identified as the sought info-chemicals. Synthesized peptides affect mate choice as predicted. Specific olfactory neurons were shown to react to these peptides but only to the anchors that define the binding specificity. Even eggs choose sperm to produce offspring with optimal MHC, though the signaling pathway needs further research.Although an individual’s mix of MHC immune genes determines its resistance, finding MHC-dependent mate choice occurred by accident in inbred mice. Inbred mice prefer MHC dissimilar mates, even when the choice was restricted to urine. It took decades to find the info-chemicals, which have to be as polymorphic as the MHC. Microbiota were suggested repeatedly as the origin of the odor signal though germ-free mice maintained normal preference. Different versions of the ‘carrier hypothesis’ suggested MHC molecules carry volatiles after the bound peptide is released. Theory predicted an optimal individual MHC diversity to maximize resistance. The optimally complementary mate should be and is preferred as several studies show. Thus, the odor signal needs to transmit the exact information of the sender’s MHC alleles, as do MHC ligand peptides but not microbiota. The ‘MHC peptide hypothesis’ assumes that olfactory perception of the peptide ligand provides information about the MHC protein in a key-lock fashion. Olfactory neurons react only to the anchors of synthesized MHC peptides, which reflect the binding MHC molecule’s identity. Synthesized peptides supplemented to a male’s signal affect choice in the predicted way, however, not when anchors are mutated. Also, the human brain detects smelled synthesized self-peptides as such. After mate choice, the lottery of meiosis of randomly paired oocyte and sperm haplotypes would often produce MHC non-optimal offspring. In sticklebacks, eggs select MHC-compatible sperm, thus prefer the best combination close to the population optimum. Immune genes of the Major Histocompatibility Complex (MHC) are by far the most polymorphic genes in vertebrates. Only one or a few different MHC alleles provide resistance to a specific parasite ,2. Each This review follows the history of studying MHC-dependent mate choice. Because most of the early experiments were performed with mice, later followed by stickleback fish, insights and ideas focused to some extent on these models and thus had limitations for being generalized. It is, however, convenient to describe the history of understanding mechanisms and functional consequences of MHC-dependent mate choice in one or two finally well-studied and understood systems rather than including the great variation among species right from the beginning. I found it convincing how the various parts of a system made sense as predicted by immunological theory. It could be the ‘null system’ which needs to be extended to cover natural variation.One sensory modality that transports the information about an individual’s MHC was revealed again in mice: odor. The choice between urine odor from MHC similar and dissimilar mice in a y-maze favored MHC dissimilar individuals e.g., ,52,53,54The puzzle of the origin of the odor and of its composition took a long time to be solved. One possibility could be that populations of commensal microorganisms generate differential odorants whose composition eventually reflects MHC diversity . The MHCBolnick et al.  showed tObviously preen oil contains an MHC-dependent odor signal. Because preen oil composition was related more strongly to MHC genotype than to preen gland microbiota overall, the authors suggested the following: the effects of MHC on the composition of preen oil are not facilitated primarily through microbiota in the preen gland . InsteadThe microbiota hypothesis experienced almost continuous ups and downs that read similar to a fascinating criminal story: Yamazaki et al.  suggesteThe results of Yamazaki et al.  and SingYamazaki et al.  comment If the ‘microbiota signaling hypothesis’ is to be revived, some proximate and functional questions need to be answered, for example : If we cIf these stringent conditions are fulfilled, it needs the study of the evolutionary processes that facilitate the origin and also the persistence of communication that is microbial-mediated, rather than chemical signals that the animal host synthesizes itself, avoiding conflict between microorganisms and the animal host ,64. BefoSeveral ideas assumed that MHC molecules are the carriers of the specific info chemicals. After an infection, the host’s cells contain foreign proteins which are degraded by proteasomes into small pieces, about nine amino acids long, called peptides. In order to inform the T lymphocytes outside the cell, the peptides need to be bound and transported through the cell membrane and presented to T lymphocytes. This is the task of MHC molecules if the peptide fits into the binding groove of an MHC molecule by its ‘anker amino acids’ in specific positions of the peptide , irrespeHowever, other info chemicals carried by MHC molecules were suggested. Evidence for volatiles that have distinctive patterns according to MHC type has been reported . CarboxyThe fact that MHC class I molecules can associate selectively with small molecules could also suggest a way for transporting a unique mixture consisting of volatile, endogenous metabolites to urine from the blood by MHC glycoproteins . AlthougHowever, Singh ,70 dismiSingh ,70 againMHC-associated peptides are cleared into the circulation, undergoing further fragmentation. The release of any bound peptides allows the now empty platform to bind a unique mixture of odorants, to be transported to the urine where they are further degraded to molecules that make up an odor that is MHC specific. “The nature of the specific odorant molecules that are bound to soluble class I molecules is unknown, although carboxylic acids may be one source” .“The problem with the carrier hypothesis is that it is difficult to imagine how binding properties of MHC molecules might be converted from being hydrophilic peptides-binding molecules to hydrophobic aromatic-binding molecules” . Even ifThe first results of mate choice experiments, e.g., Ref.  found a Theory based on immunological results predicted an optimal number of different MHC molecules per individual instead of maximizing MHC diversity ,78: withA reviewer suggested that a problem might arise in populations with large population variability . It can be predicted that cases where multiple alleles binding the same peptide in the sender will match a single allele in the receiver will be common, especially with promiscuous peptide binding to structurally heterogynous peptides. Whether evolution has solved this problem can be studied by detecting such cases with their fitness consequences. It could be hypothesized that populations with extraordinary high numbers of MHC loci ,84 have An optimal individual MHC diversity is predicted ,78,79. TExperimental mate choice studies found that female three-spined sticklebacks prefer the odor of the male that signals the possession of MHC alleles together with the female’s approach to the individual optimum as predicted ,30,31,90Why did the studies with inbred mice usually find a preference for MHC dissimilar mates, contrary to the optimality prediction? When inbred female mice had the choice between two inbred males, one being slightly more heterozygous, she can approach the optimum for her offspring only by preferring the dissimilar male, because inbreeding produces homozygous mice below the optimum. This is reminiscent of a population with low MHC allele diversity, e.g., after a population bottleneck. When this scenario was staged experimentally using wild-caught females that had only a few MHC class-IIB alleles. These females were offered the choice between water taken from tanks housing a dissimilar and a male MHC genotype that was identical to the female’s MHC genotype, both had the identical low number of MHC alleles as had the female, and the females behaved indeed similar to inbred mice and preferred the dissimilar male . StickleIn Hutteries, a North American reproductive isolate of European ancestry, fewer matches of HLA haplotypes were found between spouses than expected, implying that Hutterie mate choice within their population is influenced by HLA haplotypes, with avoidance of spouses with haplotypes that are the same as one’s own, i.e., a preference for ‘different’ . In humaAn odor signal is needed that transmits the exact information of the sender’s MHC alleles. MHC ligand peptides fulfil this requirement ,92. MHC MHC ligand peptides have the function to stimulate some specific olfactory neurons in the mouse vomeronasal organ , and alsAre MHC peptides used for social recognition? Bruce  detectedIf peptides naturally signal via odor revealing the MHC alleles of a male, it should be possible to manipulate the information of the signal by adding further peptides. Because a female stickleback prefers a male that would offer by scent MHC alleles that optimally complement her own alleles ,99, a suAs do mouse olfactory neurons, sticklebacks take only the peptides’ anchors into account. Both in sticklebacks and mice MHC ligand peptides interact as predicted with natural signals that inform about MHC. MHC peptides may be part of the natural perfume-like signals in other vertebrates including humans.Psychometric tests showed  participIn wild sticklebacks, individuals that possess more divergent MHC motifs harbored less diverse microbiota, although MHC explained roughly only 10% of microbial variation . An estiSchubert et al.  undertooPrecopulatory selection for mates with complementary whole MHC genotypes allows only poorly approaching the best match. A maternal and a paternal haplotype are randomly combined, which results from meiotic segregation among both oocytes and sperm, phenotypically unpredictable. This determines ultimately the genotype of the offspring. The lottery of random fusion of gametes can easily produce nonoptimal combinations of MHC haplotype. If the egg chooses and prefers the more complementary of the two sperm haplotypes of a male, it has an offspring that is closer to the optimum MHC diversity. The expectation that sperm may select for MHC complementarity has been hypothesized ,107,108.How does the egg decide? Sperm–egg interaction leads to cross-talks, studied in mice which clearly showed expression of MHC class II antigen on the postacrosomal membrane of the sperm head in mice. The roles of the MHC class II molecule of sperm in fertilization were studied by an in vitro fertilization (IVF) system. In the late stage of fertilization , the immuno-related molecules participated in fertilization ,111. HapThe micropyle of fish eggs, which is an opening in the coat of the egg through which sperm enter the egg for fertilization, apparently to carries specific molecules . These pWhen eggs could choose between sperm derived from MHC identical and from MHC dissimilar males, sperm derived from MHC identical males had greater success in fish ,116,117.In vitro exposure of female stickleback eggs simultaneously to equal volumes of sperm from two males, resulted in four male MHC haplotypes that were available for fertilization of each egg-haplotype, mimicking the situation with a sneaking neighbor . When thMHC-dependent mate choice was not known until 1975, when it was detected by chance in inbred mice. The further history of searching for a mechanism for signaling one’s MHC alleles to a potential partner revealed that it is odor in all species studied. The nature of the signal molecule, however, puzzled researchers for a long time. Microbiota were discussed and rejected repeatedly. Because they are controlled by the MHC, a negative correlation between MHC and microbiota diversity is appealing though inevitable even without a signaling function. A carrier hypothesis appeared in various versions centered on the binding specificity of the MHC molecule that was assumed to pick up and carry various substances after releasing its bound peptide. These substances should reflect the binding specificity of each MHC molecule, reassembled to signal an individual’s MHC diversity. The volatile metabolites that were suggested vary in relation to MHC types, but in a way that is inconsistent and complex.The ‘MHC peptide hypothesis’ is a pure form of the carrier hypothesis. It assumes that the bound peptide reflects, similar to a key the specificity of the lock, and the specificity of the binding groove of the MHC molecule. Synthesized MHC ligand peptides added to a male’s signal affect the females’ choice decisions in the predicted way. MHC ligand peptides stimulate also olfactory neurons of the mouse vomeronasal organ, as well as in the mammalian main olfactory system. Mutating the anchor residues of the synthetic peptides rendered them ineffective in influencing mate choice and in eliciting a response of olfactory neurons. Since the peptides that are bound by the MHC molecules of an individual reflect its diversity of MHC alleles, the peptides emitted by the individual could be the polymorphic signal. Because vertebrate mate choice aims at an optimally complementary mate that signals exactly its MHC alleles, too many potentially signaling microbiota species per individual cannot do the job. The microbiota hypothesis, though attractive, is not supported for various reasons. Signaling individuality by MHC ligand peptides is apparently conserved evolutionarily and thus could be the MHC signal in all jawed vertebrates. The lottery of meiosis of randomly paired oocyte and sperm haplotypes would often produce MHC non-optimal offspring. As shown in sticklebacks, eggs select MHC-compatible sperm leading to a combination close to the population optimum.A critical final conclusion: MHC-dependent mate choice may fail to be detected (i) when the assumption of preference for partners with different MHC alleles is tested although an optimal individual diversity exists in the population, and (ii) when MHC-dependent mate choice does not exist in the studied population. (i) and (ii) are undistinguishable without further study which might not have been conducted. Therefore, this review is biased because many non-fitting results might not have been published and because of my own bias of presenting a readable review by concentrating on the majority of the well-understood studies. The whole story is certainly more complex as future studies will show.


The start of the COVID-19 pandemic led the Los Angeles safety net health system to dramatically reduce in-person visits and transition abruptly to telehealth/telemedicine services to deliver clinical care (remote telephone and video visits). However, safety net patients and the settings that serve them face a “digital divide” that could impact effective implementation of such digital care. The study objective was to examine attitudes and perspectives of leadership and frontline staff regarding telehealth integration in the Los Angeles safety net, with a focus on telemedicine video visits.This qualitative study took place in the Los Angeles County Department of Health Services (LAC DHS), the second-largest safety net health system in the US. This system disproportionately serves the uninsured, Medicaid, racial/ethnic minority, low-income, and Limited English Proficient (LEP) patient populations of Los Angeles County. Staff and leadership personnel from each of the five major LAC DHS hospital center clinics, and community-based clinics from the LAC DHS Ambulatory Care Network (ACN) were individually interviewed , and discussions were recorded. Interview guides were based on the Consolidated Framework for Implementation Research (CFIR), and included questions about the video visit technology platform and its usability, staff resources, clinic needs, and facilitators and barriers to general telehealth implementation and use. Interviews were analyzed for summary of major themes.Twenty semi-structured interviews were conducted in August to October 2020. Participants included LAC DHS physicians, nurses, medical assistants, and physical therapists with clinical and/or administrative roles. Narrative themes surrounding telehealth implementation, with video visits as the case study, were identified and then categorized at the patient, clinic (including provider), and health system levels.Patient, clinic, and health system level factors must be considered when disseminating telehealth services across the safety net. Participant discussions illustrated how multilevel facilitators and barriers influenced the feasibility of video visits and other telehealth encounters. Future research should explore proposed solutions from frontline stakeholders as testable interventions towards advancing equity in telehealth implementation: from patient training and support, to standardized workflows that leverage the expertise of multidisciplinary teams. In the last few years,  systems , health  systems –9. Teleh systems –16.\Coupled to this, the Coronavirus-19 disease (COVID-19) pandemic propelled telehealth into the forefront as a clinical mechanism towards maintaining access to health care during a global shut down (as has occurred during other times of crisis) –29. HoweWith no established digital guidance in place for safety net settings prior to the pandemic, the evidence demonstrates that telehealth in health settings that care patients from underserved backgrounds will have to be monitored as implementation evolves—to understand and mitigate barriers to use. As such, studying telehealth implementation within safety net settings is critical for developing multi-level solutions that advance digital health equity. Therefore, to explore strategies and barriers to telehealth implementation in the safety net, we focused on the highest quality synchronous telehealth modality as the study case example—video visits—within the Los Angeles County Department of Health Services (LAC DHS), the second largest municipal healthcare system in the US. The objective of this study was to interview health system leadership and frontline clinical staff to understand their perspectives on, and experiences with the delivery of video visits during the COVID-19 pandemic, and to also inform subsequent telehealth implementation efforts in this safety net, and nationwide.LAC DHS forms the core of the health care safety net for indigent populations in Los Angeles County—the largest and most ethnically diverse county in the US. Over 50% of the primary care patient population is LEP –49. ThisIndividuals were recommended for interview by a study co-investigator (AA) who is the LAC DHS medical director for patient engagement and population health. Participants were nominated given their role in the implementation of video visit “pilots” at clinics across LAC DHS (spring 2020). Potential participants were emailed to inform them about the study. Participants could also nominate other stakeholders involved or leading the pilot video visits . Those who responded and accepted were scheduled for a 1-hour video or phone interview. Each participant was offered a $50 Amazon gift card for participation. The study was approved by the UCLA and LAC DHS Institutional Review Board.We based our interview guide on the Consolidated Framework for Implementation Research (CFIR), a conceptual framework that guides systematic assessment of multilevel contexts to identify factors that might influence implementation and effectiveness . The queOf 27 stakeholders that were nominated, 20 individuals accepted and these semi-structured interviews were conducted between August–October 2020. Participants included physicians, nurses, medical assistants, and physical therapists with clinical and/or administrative roles . ParticiPatient level themes corresponded to the CFIR “Outer Setting” construct, detailing conversations regarding patient needs and resources and patient influences in implementation feasibility.patient preparedness encompassed digital health barriers in the patient's context that could affect the feasibility of telehealth for the safety net. Stakeholders described barriers to use of existing digital health tools due to a “digital divide” for their populations, characterized by low digital literacy, limited broadband and/or cell phone data plans, and lack of access to Internet-connected personal devices . Other technology-specific challenges included patient usability of the LAC DHS telehealth interface and the English-only language of the current platform. Stakeholders noted that the current video visit system required multiple steps on behalf of the patient  and immediate contacts for troubleshooting problems. In these discussions, participants talked about identifying ideal staff to serve as telehealth “champions,” delineated characteristics of champions, and ways to support/reward champions, that would help in telehealth promotion and facilitation within clinics.ad hoc by physicians and other medical staff. It was stated that systematic identification of clinical visit types ideal for telehealth  could potentially be created, with algorithms or workflows to automatically match these to telehealth offerings . Participants mentioned that such efforts could save time for nurses and doctors. Staff thought that automatized offerings could promote telehealth uptake, as patients would probably be less proactive about asking for video visits, given their low baseline awarenes and knowledge about telehealth in the safety net. The other major operational workflow that participants mentioned was the need to integrate digital readiness patient screening or assessment tools as part of clinical care. During early phases of implementation, providers spent time trying to “identify” ideal candidates to offer a telehealth visit to . While this identification process was somewhat helpful to increase the yield on completed telehealth video visits, obtaining this information required extra time during the visit and limited the service to subgroups of patients. Participants brought up the potential of digital screening tools to increase immediate yield of visits and help identify patient needs and allocate resources for support. For example, a pre-visit preparation session could help make video visits more accessible to those who most needed it and troubleshoot connectivity and other problems. However, participants noted that this screening process would require a standardized tool, such as a set of validated predictor questions that could quickly and easily identify patient's needs for support. Without a uniform approach and systematic guidance, too high a burden would be placed on staff and providers.Stakeholders discussed the informal use of workflows to identify appropriate clinical scenarios for telehealth. In the video visit pilots, this was being done Themes that corresponded to the health system mostly reflected CFIR factors regarding the planning, engaging, execution, reflection, and evaluation over telehealth implementation.Among the barriers cited were lack of planning for needed equipment and ancillary resources: such as not enough computers with cameras in the clinic, lack of physical space to expand telehealth given constraints of a simultaneous in-person and telehealth visit schedule for providers in a county clinic with a shortage of clinic rooms, need for differentiating telehealth visit procedures from in-person visits , challenges with broadband Internet access in clinic such as poor Internet reception in some of the county clinics, lack of systemwide IT support to facilitate early implementation, and video visits not integrated with the system's current patient portal.Participants endorsed the importance of routine telehealth discussions between leadership, IT, and front-line staff, especially for the sharing of best operational practices, digital educational tools for patients (and staff), and patient-centered digital engagement across different sites in this large county health system. Most participants recommended that the health system invest more to support patient education that impacted preparedness for telehealth access and high quality utilization. They described feeling like they were designing these processes in real time. Additionally, although tailoring to their specific settings is needed, they would have benefited from learning about other clinical sites' models, approaches, and “mistakes,” particularly those sites that started earlier with telehealth implementation. They called for LAC DHS to develop more centralized patient and staff telehealth educational resources.Participants also discussed being “unclear” about the goals of the implementation, expectations from leadership and what telehealth “success” looked like in the safety net. Did this mean that all patients should be using video visits or a goal number or percentage of visits by some date? Would these metrics be uniform across specialties and clinic sites? The stakeholders we interviewed felt it would be important to have staff partner with leadership in asking these questions and in goal setting. They also emphasized the importance of transparency about specific telehealth goals and regular updates to their frontline staff. Participants also mentioned that these metrics should be set with the overarching aim of offering the highest quality of care possible to their patients and not for the sake of simply reaching some arbitrary telehealth uptake or usage metric at LAC DHS. Finally, participants noted that without measurable telehealth goals, objectives and metrics, there was less incentive and accountability to continue the use of video visits beyond the pilot phase.This qualitative study of informed safety net stakeholders presents some important multilevel lessons learned around telehealth implementation in settings caring for historically and contemporarily underserved patient populations. Of note, thematic narratives from these interviews highlighted the following takeaways: patients' longstanding risk for and history of the digital divide must be addressed up front, with the aid of trained multidisciplinary teams, established workflows tailored to each clinical setting that facilitate telehealth, and with clear communication and partnership between safety net leadership and on-the-ground staff about the objectives and goals for telehealth care for their patients. Most participants stressed the need for the health system to invest more resources to support patient engagement and education that impacted preparedness for telehealth access and high quality utilization. If these challenges are not addressed, this could be a set-up for worsening health disparities for these patients , already at higher risk of poor disease management outcomes.familismo” in the Latina/o/x community, a primary ethnic minority population served by LAC DHS)  . The intLAC DHS) .Our study adds new content around the readiness and culture of providers and staff to deliver telemedicine, which is not actively explored in previous literature. Participants discussed that there was almost an assumption made by leadership that frontline safety net staff interfacing the most with patients would be comfortable using these new telehealth tools. Future implementation will have to focus on the technology needs and understanding of the workforce, and staff telehealth training and empowerment for those at the front lines of the health technology implementation in the safety net . Also, mHealth system-specific challenges in the discussions encompassed technology planning barriers like usability and the English-only language of the video visit platform, which has also been previously discussed in the literature as major factors –83. PartStudy limitations included the small sample size of staff and leadership who were nominated to participate in the interviews, and limited generalizability to safety net health systems outside of Los Angeles County. This study focused on workforce and leadership stakeholder perspectives in the implementation—however, research centered around patient perspectives will be needed to validate changes, and advance substantial progress. In addition, this study did not address the relevant role of external policies like Medicaid reimbursement of phone and video visits, impact of patient-centered staff such as health educators and community health workers , and availability of telehealth platforms and technology support in multiple non-English languages—all of which have been shown to be critical factors in the sustainability of telehealth in the safety net . Future Overall, the purpose of this formative study was to generate initial health stakeholder insights regarding meaningful telehealth implementation for safety net patients and settings, as all health systems around the country are integrating remote strategies to reach out to patients, even beyond COVID-19. Although telehealth is not a full replacement for all in-person health care, it is important to note that telehealth is an added and complimentary clinical tool to address longstanding and continued health access inequities among underserved patients, if implemented appropriately in these settings. Because Los Angeles County is the largest and most ethnically diverse county in the country, these unique insights will be applicable to safety net systems across the US who are working to augment access to care and prevent worsening of chronic disease conditions among their patients. This augmented access will be especially needed after the disproportionate physical and mental health traumas inflicted upon this safety net population from COVID-19—effects that will resonate years beyond the end of the pandemic.