To explore risk factors associated with COVID-19 susceptibility and survival in patients with pre-existing hepato–pancreato–biliary (HPB) conditions.Cross-sectional study.East London Pancreatic Cancer Epidemiology (EL-PaC-Epidem) Study at Barts Health National Health Service Trust, UK. Linked electronic health records were interrogated on a cohort of participants (age ≥18 years), reported with HPB conditions between 1 April 2008 and 6 March 2020.EL-PaC-Epidem Study participants, alive on 12 February 2020, and living in East London within the previous 6 months (n=15 440). The cohort represents a multi-ethnic population with 51.7% belonging to the non-White background.COVID-19 incidence and mortality.Some 226 (1.5%) participants had confirmed COVID-19 diagnosis between 12 February and 12 June 2020, with increased odds for men  and Black ethnicity  as well as patients with moderate to severe liver disease . Each additional comorbidity increased the odds of infection by 62%. Substance misusers were at more risk of infection, so were patients on vitamin D treatment. The higher ORs in patients with chronic pancreatic or mild liver conditions, age >70, and a history of smoking or obesity were due to coexisting comorbidities. Increased odds of death were observed for men  and Black ethnicity . Patients having respiratory complications from COVID-19 without a history of chronic respiratory disease also had higher odds of death .In this large population-based study of patients with HPB conditions, men, Black ethnicity, pre-existing moderate to severe liver conditions, six common medical multimorbidities, substance misuse and a history of vitamin D treatment independently posed higher odds of acquiring COVID-19 compared with their respective counterparts. The odds of death were significantly high for men and Black people. First multi-ethnic population-based study on COVID-19 in patients with hepato–pancreato–biliary group of diseases.Systematic identification of the effect, or the lack of it, of individual demographic and clinical factors on the infection and mortality of COVID-19 in a large cohort of over 15 000 patients, robustly controlling for potential confounders in their evaluation.Access to longitudinal data from linked primary and secondary care electronic health records, and use of rule-based phenotyping algorithms allowed for improved completeness and accuracy of the explored variables.Some observed increased odds of SARS-CoV-2 infection and related death could be plausibly explained by unmeasured confounding.The effects reported in the study could be influenced by the relatively smaller size of COVID-19 cases within this cohort.COVID-19 is a novel infectious disease caused by SARS-CoV-2, with a wide-ranging disease course. Infection and mortality rates of the COVID-19 pandemic have varied widely among nations and demographics,16–18Patients with diseases of the liver, pancreas or biliary tract  are considered, in general, to be at risk of developing serious medical conditions. Expression of the ACE2 gene—a receptor for the SARS-CoV-2 virus—along the gastrointestinal tract is well documented, which suggests the digestive system is a potential route for COVID-19,The UK has been the worst affected country in Europe by COVID-19, with a reported death toll of 44 819 as of 30 June 2020.All data used for this study were collected and processed under the East London Pancreatic Cancer Epidemiology (EL-PaC-Epidem) Study at BHNT. In brief, EL-PaC-Epidem is an ongoing study that ascertains patients diagnosed or reported with HPB diseases including cancers, as well as control patients , within five BHNT hospital sites  between 2008 and 2021. The study is limited to the secondary use of a specified subset of patients’ retrospective EHR generated during the course of normal care of these patients. It links EHRs from different data sources , including primary care through general practitioners (GPs) (Discovery East London Programme data service (DDS)) and secondary or tertiary care through hospitals (BHNT Consolidated Data Extract (CDE)). Patients who have previously informed their GPs or NHS to stop sharing their personal and health records for purposes other than their individual care were automatically excluded. The current EL-PaC-Epidem Study cohort consists of 27 321 adult patients (aged 18 years or over), diagnosed or reported with at least one of the HPB conditions  between 10.1136/bmjopen-2020-045077.supp1Supplementary dataThis is a single-centre cross-sectional study using the linked EHR data of patients with a history of HPB diseases. Within this specific patient group, the study focused on the incidence of COVID-19, and examined the association of SARS-CoV-2 infection with six common medical comorbidities , lifestyle factors , and use of selected prescription medications.confirmed SARS-CoV-2 infection were identified by: (1) the presence of International Classification of Diseases 10th edition (ICD-10) or Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT) codes for confirmed COVID-19 diagnosis assigned in their hospital encounters or GP records during the observation period between 12 February and 12 June 2020  p10.1136/bmjopen-2020-045077.supp2Supplementary dataWe also examined the onset-to-death distribution within the patient group with a confirmed COVID-19 diagnosis (EL-HPB-COVID). Mortality data were collected on 12 October 2020. Following the latest Public Health England definition,codelists. For some variables, codelists also included keywords to conduct automated substring search within semistructured text as well as local laboratory test and physiological observation terms.All patient data were obtained from retrospective EHR, harmonised across hospital and GP coding systems where applicable, and organised into 40 primary variables across seven categories corresponding to the focus of the study . BHNT CDany malignant disease, and non-malignant diseases of liver, pancreas or biliary tract. Non-malignant liver diseases were further divided into mild and moderate to severe subgroups, extending the definition from CDMF Charlson Comorbidity Index,Rule-based phenotyping algorithms were developed for each categorical variable to characterise patients, integrating information from multiple sources where available to counteract bias. HPB diseases were grouped into four categories : any malindex date, otherwise they were considered negative for the condition.Phenotyping algorithms defining the comorbidities were based on diagnosis codes (presence) or semistructured text search (presence or absence), with the additional inclusion of procedural codes (presence), some observation or laboratory test results (presence) and related medication use (at least three prescriptions). Patients were considered to have or have had a specific medical condition if they met at least one criterion indicating the presence of the condition before the 2 or more. Patients assigned never status at any point but having a record of current or past status before that date were reassigned to past status. The most recent lifestyle record before or on the index date was then used to assign current, past or never status to the patients. Patients with no record of a specific lifestyle factor were classified as having missing data. Patients were assigned current, past or non-user status for medication use variables based on the number of GP prescriptions issued in the last 2 years for the medicines under specific medication groups. Patients with no record of prescription for particular medications were assigned non-user status. With at least three prescriptions issued, a patient was assigned current user status if the latest issue was within 3 months preceding the index date, and past user status otherwise. Patients with record of less than three prescriptions were classified as non-user. Patients with COVID-19 were considered to have a specific complication during admitted patient care if at least one of the hospital diagnosis codes from the complications codelist was recorded during the observation period after index date, otherwise they were considered negative for the complication. A patient was considered to have a recurrent complication if they had a history of that particular comorbidity, otherwise it was considered as a novel complication.Phenotyping algorithms defining the lifestyle factors were based on the longitudinal entries  derived from diagnosis codes and free text search, with the additional inclusion of BMI observation for obesity. Obesity was defined as BMI of 30 kg/mcodelist construction, and phenotyping algorithm development were done in consultation with a panel of clinicians and scientists . A comprehensive list of codelists and phenotyping algorithms for the study variables are available on the EL-PaC-Epidem portal (https://pac-epidem-el.bcc.qmul.ac.uk/covid-19/).Selection of study variables, 2 test, Fisher’s exact test and Kruskal-Wallis rank-sum test, as appropriate. P values less than 0.05 were considered significant. Similar descriptive analyses were performed for the EL-HPB-COVID cohort, and by survivor and deceased groups.We conducted descriptive analyses for the EL-HPB cohort as a whole, by a group for patients with confirmed SARS-CoV-2 infection and the rest . Differences in demographic and clinical characteristics between the groups were assessed with Pearson’s χTo explore the risk factors associated with COVID-19 susceptibility and subsequent survival, the effect size for each variable under investigation was evaluated with ORs with 95% CIs, using regression models with a binomial distribution. Crude ORs were obtained from univariable regression models, and then simultaneously controlled for a fixed set of potential confounders  using multivariable regression models with Benjamini-Hochberg correction for p value adjustment. The median age of the overall EL-HPB cohort being 57 years, a simplified binary age grouping  was used in multivariable regression models for comorbidity, lifestyle, medication use and post-diagnosis complication analyses. Since a participant with non-malignant HPB diagnoses for multiple organs can be represented in multiple HPB subgroups, the effect estimation for individual HPB disease variables was further mutually controlled for other HPB diseases.We also conducted more in-depth post hoc analysis to evaluate the confounding effect of pre-existing medical conditions by adding comorbidity covariates individually in the multivariable regression models. Finally, effect modification by non-malignant HPB disease subgroups was evaluated by adding interaction terms in the models and comparing them with models lacking this interaction via the likelihood ratio test. Any potential association between HPB diseases and COVID-19 susceptibility/mortality risk factors was further evaluated in stratified analyses according to the disease subgroups.Patients with missing data for individual categorical variables were included in the descriptive analyses and in regression models for effect estimation. All statistical analyses and visualisations were performed in R (V.3.5.1).Patients and the public were involved in evaluating the design of the umbrella study (EL-PaC-Epidem), particularly the notion of collection and processing of retrospective patient data without their consent. The support from NHS Confidentiality Advisory Group was obtained based on the positive opinion posed by patients and the public.The final EL-HPB cohort consisted of 15 540 patients, after applying the eligibility criteria and excluding 168 suspected but unconfirmed COVID-19 cases. By 12 June 2020, 226  confirmed cases of COVID-19 were reported in this cohort . This waBetween 12 February and 12 August 2020, the all-cause mortality rate in the non-COVID-19 group was 2.4%, whereas the rate in the COVID-19 group during the same period was 27.4% . When an10.1136/bmjopen-2020-045077.supp3Supplementary dataThe risk analyses showed a greater odds of COVID-19 for men, the Black community and those with moderate to severe liver disease . Patient10.1136/bmjopen-2020-045077.supp4Supplementary dataSubstance misusers had higher odds of infection, but the higher odds observed for those with a history of smoking or obesity were due to underlying comorbidities. Patients on vitamin D treatment and past users of ACE inhibitors were associated with higher odds of infection. The slightly reduced yet significantly high odds remained after controlling for comorbidities, with renal (for vitamin D users) and cardiovascular (for ACE inhibitor users) diseases being the principal source of the reduced estimates . Higher A small number of factors appeared to modify the association between HPB disease subgroups and risk of COVID-19 infection . In pati10.1136/bmjopen-2020-045077.supp5Supplementary dataThe risk analyses showed an increased odds of COVID-19-related death for men, individuals from the Black community and patients who had acute respiratory complications during admitted care without a history of long-standing respiratory problems . Increas10.1136/bmjopen-2020-045077.supp6Supplementary dataWe present, for the first time, data on a large, single-centre, multi-ethnic cohort of patients with HPB diseases, where primary, secondary and tertiary care EHRs were integrated to investigate the incidence and outcome of COVID-19, to demonstrate how key demographic characteristics and a range of comorbidities, lifestyle factors and medications are associated with SARS-CoV-2 infection and outcomes in patients with HPB diseases.We noted higher odds of COVID-19 in patients with prior pancreatic and liver conditions. The higher odds associated with liver conditions are consistent with earlier findings.Men had higher odds of infection and mortality than women, which is consistent with previous reports,38COVID-19 statistics have highlighted a disproportionate effect on BAME ethnic groups with an increased risk of infection and poor outcomes.All comorbidities, such as diabetes, hypertension, high cholesterol, cardiovascular disease, kidney and respiratory disease, were independently associated with an increased risk of COVID-19, whereas the presence of cardiovascular disease contributed to an added risk of death, concurring with previously reported cohort studies.Smoking leads to severe health consequences, which explains the greater risk observed in our cohort of past smokers with high prevalence of respiratory and cardiovascular diseases. However, current smoking status appeared to have a protective effect in our cohort after adjusting for comorbidities, as has been observed by others, an aspect which cannot be mechanistically explained.Although substance misuse leads to a plethora of cardiorespiratory and metabolic problems, its role in COVID-19 remains unexplored. To date, this is the first study providing a concrete measure of the risk of COVID-19 for substance misusers. Our initial results showing that substance misusers are at a heightened risk for COVID-19 irrespective of the comorbidities warrants a strong case for considering it as an independent risk factor for COVID-19, and may be related to high-risk behavioural patterns.44 45Previous studies have found a significant relationship between obesity and an increased risk of COVID-19,Concerns have been raised regarding the use of various medications with respect to the risk of COVID-19 and the subsequent outcome; and, our analyses contribute to that discussion for some of the widely used prescription drugs. The higher odds observed for the history of various prescription drugs use are consistent with the management of underlying prevalent comorbidities of the study cohort: cardiovascular conditions , cholesterol (statin), chronic respiratory diseases , or background HPB condition (PPI). An important finding from our study is the significant risk observed for vitamin D users, supportive of the possible association between development of COVID-19 and vitamin D deficiency,51 52The literature is conflicted on the potential impact of antihypertensive drugs on COVID-19, particularly those that act as inhibitors to the renin–angiotensin–aldosterone system (RAAS) and upregulate ACE2 expression, suggesting these drugs may be potential risk factors for infection,Our study also shows that recent users of anti-inflammatory drugs, namely glucocorticoid and β2-agonists, had increased odds of COVID-19 and subsequent poor outcome. Controlling for comorbidities resulted in non-significant odds of infection for these patient subgroups, indicating underlying medical conditions—particularly those of respiratory system—to be responsible for the increased susceptibility. However, the observed harmful associations between these drugs and COVID-19-related death could not be explained by a simplified binary representation of underlying six common health conditions. Glucocorticoid drugs, for instance, are used to treat many other inflammatory conditions, notably inflammatory bowel disease (IBD), whereas HPB diseases constitute some of the most common extraintestinal manifestations of IBD. It has been shown that use of corticosteroids is associated with adverse COVID-19 outcomes among patients with IBD.A key strength of our study is that we have systematically identified the effect, or the lack of it, of individual demographic and clinical factors on the infection and mortality of COVID-19 in a cohort of over 15 000 patients, robustly corrected for potential confounders in their evaluation. Our large population is highly representative of patients with HPB diseases from diverse ethnic groups, which contributes to the generalisability of our findings. Another strength is our use of linked EHRs, harmonised for variations in coding that exist between different EHR systems. We ascertained patient demographics, lifestyle, comorbidities and medications by linking hospital records with pseudo-anonymised longitudinal primary care records, which substantially enrich the data that are recorded on hospital visits.Retrospective EHR-based COVID-19 studies often suffer from incomplete or missing data on patient characteristics, including key variables such as BMI, ethnicity, smoking or pre-existing comorbidities.Our study also has some important limitations. One limitation is the risk of residual confounding or confounding by indication due to unmeasured or simplified binary representation of potential confounding variables. For example, the observed association between vitamin D users and risk of COVID-19 may be different if participants’ vitamin D level/deficiency status had been taken into consideration. Similarly, the observed association between COVID-19-related death and recent use of glucocorticoid or β2-agonists may reduce or get amplified if respiratory disease severity or other indications for corticosteroid use were considered.Another critical limitation is associated with the confirmation of East London residency for the study cohort. Patients’ addresses (current or past) are not collected under the umbrella study, which considers patients with HPB conditions (with the exception of cancer) treated or managed at BHNT hospitals as East London residents during the time of their care. The Royal London Hospital hosts one of the largest HPB centres in England, and supports patients with suspected or confirmed HPB cancer from nearby geographical areas. As the umbrella study cohort is historical, we acknowledged the probability of people moving away from East London in the meantime. In absence of a patient’s current address to confirm their residency at the outset of COVID-19 pandemic in the UK, we relied on an indirect measure to infer residency. We used a strict 6-month window preceding the study to identify a patient’s interaction with East London GPs or BHNT hospitals. Thus, we believe that any supposed reduction in the cohort size due to unaccounted change of residency within that window should have affected the COVID-19 and non-COVID-19 group in equal proportion, and hence unlikely to alter the findings we report here.Due to the rarity of the outcome (SARS-CoV-2 infection) in the full HPB cohort, the effects reported in the study could be influenced by the smaller cohort size of COVID-19 cases. We recognise that larger sample sizes of patients with COVID-19 are needed to fully understand the effect of SARS-CoV-2 in patients with HPB conditions. Our results are the first step towards this and require validation in similar national and international cohorts.We believe that the findings from this single-centre study, focusing on patients with a particular medical condition and in an ethnically diverse area, highlight some considerations that could guide clinical care while we await an effective antiviral strategy for COVID-19. The current findings reinforce our understanding of some of the important risk factors for SARS-CoV-2 infection but with regard to pre-existing HPB conditions, and allow stratification for risk, thereby providing a tool for policymakers to divert prevention as well as treatment to a clearly identified vulnerable population.


The impact of telemedicine on ambulatory care quality is a key question for policymakers as they navigate payment reform for remote care.To evaluate whether utilizing telemedicine in the first 9 months of the COVID-19 pandemic impacted performance on a diabetes quality of care measure for patients at a large academic medical center. We hypothesized care quality would reduce less among telemedicine users.Quasi-experimental design using binomial logistic regression. Covariates included age, gender, race, ethnicity, type of insurance, hierarchical condition category score, primary language at the individual level, and zip code–level income.N = 16,588) as of 3/19/2020 at a single academic health center.All adult patients younger than 75 years of age diagnosed with type 2 diabetes mellitus  systolic blood pressure less than 140 mmHg, (2) hemoglobin A1c less than 8.0%, (3) using a statin and (4) aspirin, and (5) tobacco non-use.From the pre- to post-period, the probability of meeting any given component of the composite measure for patients only utilizing in-person care was 21% lower  and for the telemedicine users 2% lower . There was an increased likelihood of meeting any given component among telemedicine users compared to in-person care alone .Patients with diabetes utilizing telemedicine performed similarly on a composite measure of diabetes care quality compared to before the pandemic. Those not utilizing telemedicine had reductions. Telemedicine use maintained quality of care for patients with diabetes during the first 9 months of the COVID-19 pandemic.The online version contains supplementary material available at 10.1007/s11606-021-07367-3. This “blend” of in-person and remote care in the ambulatory setting transformed office-based medical practice. The durability of this blended model of ambulatory care will depend on not just the changes in access,4 possible exacerbations of disparities,9 but also whether or not remote care is of the same quality as care delivered in person.The coronavirus disease 19 (COVID-19) pandemic and the subsequent public health emergency (PHE) triggered a more than twenty-fold increase in telemedicine utilization over a 2-week period in March 2020 in order to maintain access to services while mitigating the threat of possible COVID-19 transmission. As in-person visits sharply declined, the proportion of ambulatory care delivered via telemedicine (defined as both audio-only and audio-video encounters) increased to peak at nearly half of all ambulatory encounters in June 2020.10 Telehealth has been previously demonstrated to improve chronic disease management14 for small pilots of patients with diabetes. A widely cited meta-analysis included more than forty randomized trials18 mostly used telemonitoring.19 Broad populations have been studied including a randomized intervention considering quality of care domains for veterans,20 and among older, racially diverse populations.13 Despite this evidence until the COVID-19-related PHE, there has not been broad, population-wide telemedicine utilization, and previous studies were subject to the generalizability issues inherent in smaller demonstrations.The expansion of telemedicine during the PHE was supported by many temporary waivers of telemedicine regulations by the Centers for Medicare and Medicaid Services (CMS) to increase capacity, expand workforce, reduce administrative burden, and otherwise expand telemedicine services.21 which was recently incorporated in the most recent CMS physician fee scale.22 Our study objective was to evaluate the impact of remote audio-video encounter utilization on the quality of care for patients with diabetes at a large academic medical center in the first 9 months of the PHE.23The Medicare Payment Advisory Commission (MedPAC) has recommended continuation of coverage for telemedicine for 1–2 years after the end of the PHE in order to gather data on access, quality, and cost of care,We analyzed electronic medical record (EMR) data for all patients who were identified by our institutional population registry as having type 2 diabetes mellitus (DM) as of March 19, 2020. We abstracted the following variables from our institution’s electronic medical record (EMR) at the individual level: decade of age, gender, race, ethnicity, category of insurance , systolic blood pressure, hemoglobin A1c, aspirin and/or statin prescription, smoking status, ambulatory visits to primary care, endocrinology, and other department of medicine visits, as well as hierarchical condition category (HCC) score. We also included income information from the American Communities Survey 2018 5-year estimates at the five-digit zip code level.24 We defined two sequential pre-periods of the same duration in the 18 months prior to the declaration to identify if pre-pandemic quality of care trends were parallel.We used a quasi-experimental (difference-in-differences) design. We defined our post-period to include the 9 months following the declaration of “safer-at-home” orders in Los Angeles County on March 19, 2020.N = 21,460) consisted of all patients identified by institutional clinicians as having type 2 diabetes mellitus when added to the electronic medical record problem list. This is verified for accuracy by the institutional quality team. Two physicians, one registered nurse, and two non-clinicians independently verify a random sample of patients identified as having type 2 diabetes mellitus. The study population was restricted to align with quality reporting standards, restricting to include adult patients under age 75 who are not currently enrolled in hospice care .Our study population systolic/diastolic blood pressure less than 140/90 mmHg, (2) hemoglobin A1c less than 8.0%, (3) active prescription for statins and/or(4) aspirin or other anti-platelet agents if not contraindicated, and (5) tobacco non-users or those that quit during the study period.23 We made pre-specified changes to the composite for the purposes of our analysis. Due to limitations in our EMR, we did not exclude patients who may have a contraindication for anti-platelets or consider other anti-platelet agents  as meeting this measure criterion, and did not analyze diastolic blood pressure as the proportion of patients with diastolic-only hypertension is negligible. We also did not exclude patients who became pregnant during the study period and were not able to ascertain deaths in our cohort.We defined our outcome for quality of care for patients with diabetes using the same domains as indicators included in the CMS Diabetes Composite quality measure from the CMS Measures Inventory.N = 6,405) or an endocrinologist  to define our total exposure group . Telemedicine visits are defined at our institution using the (EPIC/Clarity) visit types as recorded in our EMR, and distinguish between telephone encounters, new video visits, and return video visits. Visit type codes are unique to the EMR instance but available on request.We identified all included patients with at least one telemedicine visit in the post-period to either a primary care clinician , hierarchical condition category (HCC) score, all at the individual level. We also included income information from the American Communities Survey 2018 5-year estimates at the five-digit zip code level.Our study protocol was approved by the UCLA Institutional Review Board via expedited review.Using a binomial regression model, we estimated the effect of telemedicine use (at least one encounter in primary care or endocrinology) by comparing the likelihood of meeting any individual component of the diabetes composite outcome in the 9 months before and after March 2020 between the exposure and control group. All models included as covariates the sociodemographic and clinical characteristics described above. We performed several sensitivity analyses including 1) meeting all five component indicators of the diabetes composite measure, and sequentially fewer  indicators, (2) meeting four component indicators omitting the systolic blood pressure variable, which we hypothesized would be difficult to assess via telemedicine, and (3) a subgroup analysis of patients receiving Medicare benefits (either through disability or over the age of 65 years) and meeting 4/5 indicators given hypothesized challenges of older and disabled patients in accommodating new technology . Our binomial regression model was specified by using the STATA command “binreg”, and all sensitivity analyses were using logistic regression (“logistic”).N = 224, 1%) and most patients utilizing telemedicine in the post-period also had in-person appointments . Both audio-only utilization  and audio-video utilization  increased dramatically in the post-period. Of audio-only utilizers, 66% were exclusively audio-only  telemedicine utilizers in the post-period. Telemedicine utilizers varied from those not utilizing telemedicine as less likely to have commercial insurance, more likely to be insured through Medicare and have lower HCC scores . These patients were more likely to be female, Latino/a, more likely to be insured through Medicare and an institutional managed care plan, and have lower HCC scores , whereas patients utilizing telemedicine were no less likely . The interaction between time period and use of telemedicine services was significant , as well as the individual-level covariates age (by decade of life), gender, self-reported Asian or other race, and the zip code–level covariate income  , we saw significant declines  in both the in-person care and telemedicine utilizing groups  with non-significant differences between the groups . Similarly, among patients with an HCC score of 2 or more , we observed a reduction in those meeting 4 of 5 indicators among patients receiving in-person care alone  although not among those patients utilizing telemedicine services , and the difference between the groups was not statistically significant . Few patients with an HCC score of 2 or more utilized telemedicine (N = 946). Full covariate estimates for sensitivity analyses are available in a supplementary appendix . Similarly, patients utilizing telemedicine were as likely as those using telemedicine to meet the remaining quality indicators when the blood pressure measurement component of the composite was excluded  , which may be improved with advances in remote patient monitoring. This disruption has been also seen in national cohorts. Our study is not without limitations. First, our data were from a single institution in a large urban environment, and limitations to the use of telemedicine (such as broadband access or technology limitations) may be less prevalent in our study population than in a predominantly low-income or rural population. Second, our intervention included all patients with at least one telemedicine encounter in the 9 months following the pandemic, and while this was the first opportunity to study population-wide telemedicine implementation, the time was uniquely transitional as “safer at home” orders were enacted, vaccines were developing, and case rates in our home county and state varied widely, perhaps leading to unobserved variable biases not controlled for in our detailed model. Third, part of this first population-wide implementation of telemedicine is the acknowledgement that despite observed variable consistency in diabetes care among pre- and early-pandemic telemedicine utilizers, the population using telemedicine before the pandemic may have varied from the general population at our institution on unobservable characteristics.In conclusion, the rapid expansion of telemedicine utilization has transformed ambulatory care delivery during the COVID-19 pandemic, and improved access to care to populations attempting to minimize exposure to a deadly respiratory pathogen. This unprecedented change in the mode of ambulatory care delivery has many unanswered questions currently pressing policymakers. We found that in a single institution, the utilization in the 9 months following the COVID-19 pandemic improved the quality of care for patients with diabetes. Future studies are needed to validate these results in state- or nation-wide populations, and with additional chronic diseases, in order to make evidence-based policy regarding the continuation of telemedicine coverage after the public health emergency concludes.ESM 1(DOCX 39 kb)ESM 2(DOCX 7348 kb)


Most of the previous research on recycled concrete aggregates (RCA) has focused on coarse RCA (CRCA), while much less has been accomplished on the use of fine RCA particles (FRCA). Furthermore, most RCA research disregards its unique microstructure, and thus the inferior performance of concrete incorporating RCA is often reported in the fresh and hardened states. To improve the overall behaviour of RCA concrete advanced mix design techniques such as equivalent volume (EV) or particle packing models (PPMs) may be used. However, the efficiency of these procedures to proportion eco-efficient FRCA concrete still requires further investigation. This work evaluates the overall fresh  and hardened states  performance of sustainable FRCA mixtures proportioned through distinct techniques  and incorporating different types of aggregates  and manufacturing processes . Results demonstrate that the aggregate type and crushing process may influence the FRCA particles’ features. Yet, the use of advanced mix design techniques, particularly PPMs, may provide FRCA mixes with quite suitable performance in the fresh  and hardened states  along with a low carbon footprint. Concrete is a widely used material for critical infrastructure worldwide; over 10 billion tons of concrete are produced annually in the modern industrial society ,3,4. AmoThe intrinsic difference between RCA and natural aggregate (NA) is the fact that CRCA is a two-phase material composed of the original virgin aggregate (OVA) and residual mortar (RM). Likewise, fine recycled concrete aggregates (FRCA) comprise the original virgin aggregate (OVA) and residual cement paste (RCP). The properties of RCA concrete made of CRCA have been extensively investigated ,15,16,17Studies have demonstrated that mortar mixtures made of partial or full direct replacement of NA by FRCA displayed more somewhat similar fresh state behaviour than conventional mortar, once both aggregates (either NA or FRCA) were in saturated surface-dry conditions . ConversIn this context, advanced mix design techniques have been developed to optimize recycled concrete mixtures, allowing more efficient re-use of RCA in concrete and enabling better performances in the fresh and hardened states. The literature suggests that the key factor for an efficient proportioning of recycled concrete mixtures bearing CRCA is to account for their unique microstructure , while the mix design and proportioning techniques such as the equivalent mortar volume (EMV)  and equi3) and chemical admixtures [One of the earliest attempts to use a mix proportion of RCA concrete was performed through direct replacement methods (DRMs), which can be conducted by weight or volume. This approach treats RCA as homogeneous material and partially replaces a certain amount of natural aggregates accounting for their distinct microstructure and or the presence of RM ,34. Moremixtures ,37. In omixtures . Hence, The equivalent mortar volume (EMV) method was initially proposed by Fathifazl et al. 2009a and treated RCA as a multi-phase material composed of RM and OVA. Thus, the volume of cementitious materials added to the recycled mix is reduced according to the amount of existing RM content adhered to the RCA particles. It has been suggested that EMV can reach similar or even somewhat higher compressive and tensile splitting strengths than conventional concrete ,40. BesiIn order to address the issues often faced in the fresh state by EMV-proportioned RCA mixes, especially in eco-efficient mixtures with a reduced binder content, a modification to the preliminary method was proposed by Hayles et al. 2018. The EMV-mod method adds a supplementary factor to the previous strategy to optimize the “cement-to-sand mass ratio” of the RM and thus allows the selection of the amount of cement to be accounted for in the new RCA mix. Hence, EMV-mod-proportioned mixtures show better improvement in fresh-state performance  than EMV mixes. However, this approach was verified to present an important drawback since the binder content is typically increased for a given targeted strength compared to conventional and EMV-designed mixes .3) due to the significant increase in fine aggregates and decrease in coarse particles in the system [Recently, a new mix design procedure, the so-called equivalent volume (EV) method, was developed by Ahimoghadam et al. 2020 based on the main concepts of the previous EMV and EMV-mod methods. The EV was established to solve the issues faced by EMV and EMV-mod mix-proportioned mixtures in the fresh state, along with providing recycled mixtures with an eco-friendly character and suitable performance in the hardened state . The nove system ,41.Particle packing models (PPMs) are advanced mix design techniques used to improve the performance of concrete mixtures in fresh and hardened states. PPMs are divided into discrete and continuous models; either discrete or continuous, PPMs aim to optimize granular systems’ particle size distribution (PSD), reducing the material’s porosity and consequently increasing the system’s packing density . The disq) and the largest particle size (D) [q) along with the largest (LD) and smallest (SD) particle sizes  present in the system (Equation (1)). The coefficient of distribution (q) is adopted based on the fresh-state requirements of the mix; values ranging from 0.20 to 0.23 are often selected for self-consolidating mixtures, whereas distribution factors of 0.26–0.28 are normally targeted for vibrated and or pumped concrete. It is worth noting that 0.37 is the q value that yields the highest packing density, hence the lowest porosity to granular systems [PD, and PD is the particle size.The first continuous PPM was established by Fuller in 1907, and it is based on a power curve that accounts for two variables: the distribution factor (size (D) . Over th systems .(1)CPFTPPMs have been widely and successfully used to improve performance, especially in the hardened state of eco-efficient ,52, convAs previously described, there is currently limited research on the influence of the FRCA particle features  and mix design techniques  on the fresh- and hardened-state performance of eco-efficient recycled concrete mixtures made of 100% FRCA. This work is divided into two main phases: (1) production and characterization of FRCA materials and (2) appraisal of the fresh- and hardened-state properties of eco-efficient FRCA concrete mixtures. The first phase evaluates the impact of the FRCA type  and manufacturing process  on the physical properties of the granular material. In the second phase, three mix design techniques  are selected to proportion eco-efficient FRCA mixtures made of natural or manufactured sand. Finally, evaluations on the fresh- and hardened-state properties are conducted, and comparisons with a companion conventional concrete (0% FRCA) are performed. It is worth noting that the term eco-efficient used in the context of this work refers to concrete mixtures displaying equal or lower binder contents than their companion conventional mixtures. In other words, there is no need to use a supplementary amount of binder to obtain a performance in the recycled mixture as is conventionally adopted in RCA research.The experimental program is divided into two main streams as described in 3 and 0.75% absorption was used to produce the conventional concrete mixtures. Neither chemical admixture nor mineral admixtures were employed in the conventional concrete mixtures. The FRCA used in this work was manufactured in the laboratory; it is derived from crushed companion conventional concrete specimens, mix-proportioned through the ACI method  and displaying a design compressive strength  of 35 MPa. Two families of FRCA were fabricated, one containing a natural siliceous sand (ACI-NS) and the other incorporating a limestone-manufactured sand (ACI-MS). A coarse limestone aggregate with a nominal maximum size of 19 mm, an oven-dry specific gravity of 2.78 g/cmTwo hundred conventional concrete cylinders  were cast from each of the concrete mixtures used in this research incorporating NA and MS. The specimens were kept in the moulds at laboratory temperature, demoulded after 24 h and moist-cured over 28 days. In order to appraise the influence of the crushing process on the FRCAs’ inner quality, two manufacturing methods  were employed to produce the recycled granular material. The second method The RCP was measured in this work on all FRCA materials through the soluble silica sub-procedure according to ASTM C1084-15  and C114Potential of RCP for further hydrationIsothermal heat conduction calorimetry (IHCC) of the FRCA was determined in an isothermal calorimeter G-563-62-L0071/AD by Controls Group. The test was performed to determine whether the residual cement paste (RCP) adhered to the FRCA particles might have some potential for further hydration in concrete. The test was conducted on original FRCA particles and cement powder for comparison purposes. It is worth noting that IHCC was performed on freshly prepared samples to avoid the possible reaction of unhydrated cement with moisture from the air. Ten grams of each FRCA material were selected for testing; 3.5 g of double-deionized water was added to the samples to evaluate the cementing capability of the RCP encountered in the FRCA particles. After mixing for 60 s, the samples were placed in the calorimeter and tested. It is important to note that the plastic scintillation vials were filled with 26.49 ± 0.2 g of glass beads as a reference. All the IHCC results are presented on the same basis (per gram of cement) since the amount of cement in each sample is variable. The IHCC results obtained in this work are presented in the analysis and discussion section.Specific gravity and water absorptionThe specific gravity and water absorption capacity of all FRCA materials were evaluated according to the method proposed by . The conParticle size distribution (PSD)A general-use  Portland cement was used in all mixes. In addition, a limestone filler with a smaller PSD than PC , known aA total of three distinct concrete mixtures  with 100% replacement of fine NA by FRCA were designed. Moreover, two control mixes  containing NS or MS were also produced for comparison purposes. Concrete mixtures proportioned using the DRM method were designed according to the ACI protocol , purposely treating FRCA as presenting the same properties of fine NA; the latter is a common practice adopted in the construction industry.The EV method  was adapw/c) of 0.35 was adopted for all FRCA mixes since preliminary trial batches indicated the need to reduce the w/c of the FRCA mixtures to yield close compressive strength results  to companion conventional concrete mixes with w/c of 0.47. Moreover, the consistency of the mixture  was aimed to lie within 100 ± 20 mm. A summary of all mixtures is presented in The DRM-, EV- and PPM-designed recycled mixtures were proportioned with 100% FRCA replacement from the four FRCA sources previously mentioned. The target 28-day compressive strength was selected as 35 MPa as per CSA  for the 3). Conversely, since the EV and PPM methods account for the RCP attached to the FRCA particles, the mixtures proportioned by these procedures presented a much lower PC content. In the case of the EV method, it was possible to obtain mixtures with Portland cement contents (≈373 kg/m3) very similar to those of conventional concrete designed with the ACI method . Likewise, mixtures designed through the continuous PPM technique (distribution factor of 0.28) and with the use of inert fillers yielded final Portland cement contents ranging from 333 to 299 kg/m3 .The mixes proportioned using the DRM method  treated the FRCA material as the same as natural fine aggregates, resulting in mixtures with high amounts of PC . The IBB rheometer a consistThe rheological profiles of the mixtures evaluated were determined with a two-step process: an increase in shear rate up to approximately 43 RPM, followed by a decrease period at the same stepwise, keeping a constant rotation for roughly 10 s at each step b. The teThe evaluation of hardened-state properties was performed through compressive strength and non-destructive tests. For compressive strength, three samples of each mixture were tested over time  as per CSA A23.1-14 . LikewisThe microstructure quality of the concrete specimens was evaluated using scanning electron microscopy (SEM). The selected samples were first cut using a diamond-bladed masonry saw followed by subsequent polishing using a mechanical polishing table with grits of 30, 60, 140, 280 (80–100 µm), 600 (20–40 µm), 1200 (10–20 µm), 3000 (4–8 µm), 10,000 (2–4 µm) and 20,000 (1–2 µm). After that, the polished sections were dried at 60 °C for 24 h. Once the polishing process was completed, the samples were examined in a Jeol JSM- 6610LV SEM operated under a low vacuum, with an electron acceleration voltage of 20 kV and a spot size of 57. Backscattered electron (BSE) was conducted at different magnifications  to study the mixture’s quality, morphology and distribution. The SEM images and the description of the microscopic features observed in the different recycled concrete mixtures are presented in the discussion section of the manuscript.3); yet, the ACI-NS resulted in a higher slump (110 mm) than ACI-MS (95 mm). Moreover, although the DRM mixtures were produced with the same water content as ACI mixtures, admixtures were required  to achieve the target slump (100 ± 20 mm). Otherwise, a lower amount of water  was used for all EV mixtures along with a 0.32% of mid-range/HRWR. The PPM mixtures achieved the required slump with the lowest amount of water  and a somewhat higher mid-range/HRWR  when compared to the EV mixtures. Finally, it is worth mentioning that mixtures containing FRCA-FG yielded overall higher slump values when compared to FRCA-CF.The consistency results  of ACI, DRM, EV and PPM mixtures are presented in The rheological profiles for the ACI, EV and PPM mixtures are presented in Analyzing the plots, one first verifies that all mixtures yielded a shear-thinning behaviour, i.e., decrease in viscosity (slope of the torque vs. rotation curve) as a function of the torque applied regardless of the mix design procedure adopted. Second, the PPM mixtures displayed the lowest yield stress, i.e., requiring a lower amount of torque to enable flow , followed by EV (7.32 N.m to 11.33 N.m) and ACI (10.70 N.m to 14.81 N.m)-mix-designed mixtures. Moreover, besides the rheological profiles and the minimum torque values mentioned above, two “extra” key rheological parameters can also be extracted . A summary of all these values is displayed in Finally, the time dependency (thixotropic vs. rheopexy behaviour) of all mixtures was also evaluated by calculating the hysteresis area under the torque vs. rotation curve. Overall, all mixtures presented positive HA, corresponding to a thixotropic behaviour; in other words, the viscosity of those mixtures decreases over time under constant shear stress or shear rate. ACI mixes presented the lowest HA values, followed by PPM and EV. Furthermore, mixtures made of MS presented lower HA than those with NS, whereas mixtures made of FG aggregates also yielded lower HA values when compared to CF mixes.In this section, compressive strength (CS) and non-destructive tests results are presented for all mixtures manufactured in the laboratory. Comparing the results, one verifies that the highest compressive strength values were obtained by PPM-proportioned mixtures , whereas the mixtures proportioned via DRM yielded the lowest results . EV-designed mixes’ results lay between PPM and DRM mixtures . The control mixes designed with natural (AC-NS) and manufactured (ACI-MS) sands presented 28-day compressive strength results within the range of 35 to 40 MPa.The compressive strength results mentioned above correlate quite well with surface electrical resistivity a and theanalysis and discussion section will be divided into six sub-sections. First, a discussion of the influence of the raw materials and manufacturing process on the FRCA features is conducted. Second, a volumetric fraction evaluation of the various recycled mixtures components obtained through distinct mix design techniques is performed, followed by their impact on those mixtures’ fresh and hardened states. Finally, microstructure analyses of the recycled mixtures are conducted, along with a discussion on the binder efficiency of FRCA mixtures proportioned using distinct mix design techniques.As previously mentioned, the present work is divided into two main parts: (1) production and characterization of FRCA materials and (2) appraisal of the fresh- and hardened-state properties of FRCA concrete mixtures proportioned using distinct mix design techniques. Although the data from the characterization of the FRCA, such as RCP content, specific gravity and water absorption and particle size distribution, were displayed in the experimental program section (since they were needed to design and manufacture the various recycled concrete mixtures), a global discussion on the obtained data seems appropriate herein. Therefore, the current The analysis of the characterization results demonstrates an important role of the raw materials used  or the RCA’s manufacturing processes  in the fresh and hardened states of FRCA concrete. Amongst the distinct properties appraised , the RCP content showed an important influence of the raw material since FRCA made of MS presented a higher RCP than FRCA made of NS . This result is likely due to the rougher texture and more angular surface of the MS material, which may enhance the bond between the cement paste and aggregates. Likewise, comparing the FRCA’s manufacturing processes, CF-made materials yielded 23% higher fineness modulus and 30% more RCP attached (on average), which is linked to the number of crushing processes, i.e., the higher the number of crushing cycles, the lower the amount of RCP attached to the fine aggregate particles. Consequently, FRCA-CF presented 4% lower specific gravity and 20% higher water absorption than FRCA manufactured through the FG crushing process.From the particle size distribution of the FRCAs, it was verified that a higher number of crushing cycles  produces a greater amount of fine material . In other words, an appropriate and optimized process is required to produce FRCA to minimize waste generation  along with energy consumption during the manufacturing process. Otherwise, FG manufacturing processes generate FRCAs with 29.1% less RCP content (on average) than CF. Moreover, the greater the amount of RCP adhered to the particles, the lower the quality of the materials, and the more challenging it is for FRCA concrete mixture proportioning to achieve comparable fresh- and hardened-state properties to conventional companion mixtures.The above discussion indicates that high amounts of RCP adhered to the FRCA particles may lead to a lower-quality material since more inner deterioration such as microcracks and flaws is expected. Conversely, the presence of RCP, depending on the condition of the cement grains , may stimulate further hydration, which could help seal pre-existing inner cracks and thus enhance the overall quality of the FRCA material. In this regard, isothermal calorimetry was performed to quantify the flow and the amount of the heat released from the FRCA materials as mentioned in The calorimetric measurements indicate that the overall acceleration of exothermic reactions from FRCAs was strongly reduced compared to general Portland GU-type cement samples. The FRCAs’ heat flow curves are not very well defined. Yet, two phases were identified , which is a very different behaviour compared to the traditional GU cement behaviour with clear initial induction, accelerating and decelerating periods. Moreover, the results demonstrate that the difference in raw materials  does not significantly influence the amount of heat released over the first 92 h of the test. Yet, both FRCAs demonstrated some hydraulic activity. The cumulative heat achieved by the FRCA materials after 92 h corresponded to about 15% of the heat released by the GU-type cement. This behaviour dos not significantly change the mechanical properties of the FRCA concrete over time, but this demonstrates that further hydrates might be theoretically formed in the system, which could contribute to an increase in the overall quality of the FRCA concrete. Further analysis is still required in future projects to quantify this potential aspect more precisely.The distinct mix design methods used in this research played a very important role in the volumetric fraction components of both FRCA and CC mixes, as expected; yet, to better visualize this influence, c). These authors developed an analytical model to determine concrete mixtures’ yield stress (τc) based on the slump test results. Analyzing the data below and the experimental comparison between slump vs. minimum torque, the calculated yield stress (τc) also decreases with the increase in a slump, which attests to the validity of the minimum torque results gathered.All mixtures assessed in the study were designed with a targeted slump range of 100 ± 20 mm, being thus considered (in practice) as “workable” mixtures to be used as cast-in-place/vibrated concrete. Yet, although similar consistencies  were selected for all mixtures, quite variable minimum torque results, ranging from 4.74 N.m (PPM-NS-FG) to 14.81 N.m (ACI-MS), were obtained. In general, the higher the slump value, the lower the minimum torque required . To atteτ is the shear stress, τ0 is the yield stress, HBk is the viscosity constant of Herschel–Bulkley, and n is the flow behaviour factor, which is n < 1 for suspensions presenting shear-thinning behaviour and n > 1 for shear-thickening ones [According to Bingham’s model, the rheological behaviour of conventional concrete mixtures is described very often ,67 and iing ones . It is wHB constant was also observed to yield the lowest values for PPM mixes compared to EV and CC mixtures. It is important to notice that the higher kHB values, the higher the slope of the rheological profile curve .Analyzing the data gathered through Herschel–Bukley’s model  and plotThe above results suggest that the PPM-proportioned mixtures have the most suitable rheological behaviour for vibrated and or pumped applications. Moreover, following the study on the minimum torque, the derivative of the Herschel–Bulkley model of each concrete mixture  was perfw/c ratio; these results are due to the lower amount of RCP adhered to the FRCA-FG particles along with their more angular in shape and rougher in texture characters. Moreover, an increase of nearly 53% in CS and 31% in ER was obtained for PPM-designed mixes, whereas a slight average increase of about 16% and 6% was observed for EV and DRM mixes, respectively. The above results suggest that the FRCA particles’ features  are more important in mixtures with a more optimized particle size distribution (improved granular skeleton) and thus have lower porosity. Conversely, the raw-material type  does not seem to influence the mechanical properties of FRCA concrete significantly.The type of FRCA material  was found to have a low impact on the surface electrical resistivity (ER) and compressive strength (CS) of DRM and EV mixes and a more significant influence on the PPM-mix-proportioned mixtures. It is well known that the mechanical properties of concrete are directly related to the quality of its microstructure. Moreover, the results of CS and ER are quite well correlated; overall, the higher the compressive strength of the concrete, the higher the electrical resistivity. In general, the mixtures proportioned with FRCA-FG aggregates showed higher strength and ER results for the same Another important discussion to be addressed is on the dynamic elastic modulus (DEM) obtained in this research. The DEM results for the FRCA concrete mixtures follow a close correlation with the compressive strength, i.e., the higher the CS, the higher the DEM values. However, only the PPM-NS-FG and PPM-MS-FG mixtures could reach similar values to the companion conventional concrete mixtures . These findings may be justified by a thorough evaluation of the FRCA mixtures compositions. For instance, the replacement of natural fine aggregate by FRCA introduced theoretically more interfacial transition zones (ITZ) to the system, which may have governed (and lessened) the overall DEM of the recycled mixture. On the other hand, PPM-mix-designed recycled mixtures presented a higher DEM; this is associated with a better microstructure quality  of PPMs systems, enhancing the stiffness response of concrete mixtures as previously reported by ,69. MoreThe above discussion confirms both the influence of the manufacturing process  and the mix-proportioning technique  on the mechanical properties of FRCA concrete.w/c ratio) of the mixture [It is well established that the mechanical behaviour of CC depends on the quality of its compounds, such as hydrated products and the ITZ, which in turn is directly related to the porosity  presented a much-enhanced microstructure when compared to EV or DRM proportioned mixes since suitable (and better) adherence between the residual cement paste (RCP) and the new cement paste (CP) was observed in all samples. Moreover, minor microcracks were identified within the RCP in both PPM-proportioned mixtures (highlighted areas in 3) required to obtain one unit of a given mechanical property; for example, 1 MPa of compressive strength at 28 days. 3).In order to evaluate the eco-efficiency of conventional concrete mixtures, Damineli et al.  developebi factor was calculated for all of them, and the results are illustrated in bi values (8.3 kg∙m3∙MPa−1 with an approximate average 28-day compressive strength of 53 MPa). Furthermore, one may notice that some PPM mixtures are quite close to the bottom line of the plot , which represents the lowest amount of Portland cement conventionally used in the market for conventional concrete. Otherwise, conventional concrete mixes presented an overall bi factor of 10 kg∙m3∙MPa−1 for an average 28-day compressive strength of about 37 MPa, while DRM and EV mixes displayed bi factors of approximately 25 and 13.1 kg∙m3∙MPa−1 for average compressive strengths of 20 and 29 MPa, respectively. These results demonstrate the promising character of PPM techniques in creating mix proportions of eco-efficient FRCA concrete with suitable fresh- and hardened-state properties.To evaluate the binder efficiency of all conventional concrete and FRCA mixtures studied in this experimental program, the It is clear that the manufacturing  process influences the overall quality of the FRCA material. With only two consecutive series of crushing, the so-called CF generates recycled particles with coarser PSD, and high amounts of adhered RCP. Yet, multiple crushing series, the so-called FG, were observed to produce FRCA particles with similar PSD to natural aggregates and displayed less RCP attached to the particles due to further separation of mortar during crushing. Moreover, CF particles seem to be more rounded in shape and smoother in texture when compared to FG particles.The fresh-state behaviour of FRCA mixtures proportioned through both EV and PPM methods demonstrated an interesting performance, showing a shear-thinning profile . Yet, PPM-mix-designed FRCA concrete demonstrated the best rheological variables  among all mixtures; the latter indicates its suitability for applications under high-torque regimes such as pumping and or vibrating processesInteresting hardened-state properties  were achieved using both EV and PPM techniques. However, in general, the DRM method yielded the worst mechanical performance obtained in this work. Yet, PPM-mix-designed FRCA proved to be the most promising mix design technique to proportion FRCA concrete mixes with suitable mechanical properties, binder efficiency and an enhanced microstructure .It seems that both the aggregate types (NS vs. MS) and crushing processes (CF vs. FG) play an important role in the overall FRCA quality  along with fresh- and hardened-state performances. Yet, the results obtained in this experimental campaign demonstrated that the mix design procedure adopted to produce FRCA concrete is even more important than the FRCA features and inner quality.Finally, microscopic analysis needs to be assessed considering distinct FRCA concrete mixes through the use of both EV and PPM methods in order to investigate the different failure mechanisms of FRCA concrete, especially when subjected to harsh environmental conditions. This would propose valuable remarks on the mechanical and durability-related properties of FRCA mixes against CC mixes as well as potential improvements on the EV mixes.The current research aimed to understand the overall behaviour of FRCA concrete made of distinct raw materials , manufacturing processes  and mix design techniques . The main findings of this research are presented hereafter:


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused a pandemic of coronavirus disease 2019 (COVID-19) and is threatening global health. SARS-CoV-2 spreads by air with a transmission rate of up to 15%, but the probability of its maternal–fetal transmission through the placenta is reported to be low at around 3.28%. However, it is still unclear that which tissues and developmental periods hold higher risks and what the underlying molecular mechanisms are. We conducted an integrated analysis of large-scale transcriptome and single-cell sequencing data to investigate the key factors that affect SARS-CoV-2 maternal–fetal transmission as well as the characteristics and effects of them. Our results showed that the abundance of cytomegalovirus (CMV) and Zika virus (ZIKV) infection-associated factors in the placenta were higher than their primarily infected tissues, while the expression levels of SARS-CoV-2 binding receptor angiotensin-converting enzyme II (ACE2) were similar between lung and placenta. By contrast, an important SARS-CoV-2 infection-associated factor, type II transmembrane serine protease (TMPRSS2), was poorly expressed in placenta. Further scRNA-Seq analysis revealed that ACE2 and TMPRSS2 were co-expressed in very few trophoblastic cells. Interestingly, during the embryonic development stages, the abundance of ACE2 and TMPRSS2 was much higher in multiple embryonic tissues than in the placenta. Based on our present analysis, the intestine in 20th week of embryonic development was at a high risk of SARS-CoV-2 infection. Additionally, we found that during the fetal development, ACE2 and TMPRSS2 were enriched in pathogen infection-associated pathways and may involve in the biological processes related to T-cell activation. In conclusion, our present study suggests that though the placenta provides a good physical barrier against SARS-CoV-2 infection for healthy fetal development, multiple embryonic tissues are under risks of the virus infection, which may be adversely affected once infected prenatally. Therefore, it is necessary to enhance maternal care to prevent the potential impact and harm of SARS-CoV-2 maternal–fetal transmission. Toxoplasma gondii, HIV, rubella, cytomegalovirus (CMV), herpes simplex virus (HSV), hepatitis B virus (HBV), and Zika virus (ZIKV). These viruses can transmit vertically from mother to fetus through the placenta and infect certain fetal organs (Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused a worldwide outbreak of coronavirus disease 2019 (COVID-19) and posed a serious threat to public health all over the world. Different from general population, pregnant women often develop a special condition of immune tolerance and may be more susceptible to various infections . Common l organs . For exal organs . CMV hasl organs . Maternal organs . Recent l organs . This raIn early small-scale studies of pregnancy complicated with COVID-19, no cases of maternal–fetal transmission were observed . HoweverThe general steps of virus infecting and crossing the placenta include host receptor/co-receptor recognition, uptake into cells of placenta, and hijacking cellular processes for viral replication . It is rThe successful entry of SARS-CoV-2 into host cells depends not only on the receptor, but also on an important SARS-CoV-2 infection-associated factor, the type II transmembrane serine protease (TMPRSS2), for S protein priming . TherefoGenerally, SARS-CoV-2 mainly spreads through the air, infects into the lung, and causes substantial respiratory pathology as ACE2 is highly expressed in lung alveolar cells . On the To answer these questions, we conducted an integrated analysis of large-scale transcriptome sequencing data of multiple tissues in normal people and during fetal development and single-cell sequencing data of the maternal–fetal interface. We aim to investigate the expression levels and changes of ACE2 and TMPRSS2 in different tissues and periods of fetal development and their potential functions, to uncover the characteristics and effects of maternal–fetal transmission of SARS-CoV-2.The expression matrix of the bulk RNA-Seq data containing FPKM values for 20,050 genes in 27 tissues was downloaded from The microarray data of placenta at different stages of pregnancy were downloaded from GEO under the accession number GSE9984 of The single-cell RNA-Seq data of maternal–fetal interface are deposited at ArrayExpress, with experiment codes E-MTAB-6701 . The genThe bulk RNA-Seq data in 6 tissues between the 10th and 20th week of fetal development  can be dThe gene expression matrix contains unique molecular identifier (UMI) count was converted to Seurat object using R package Seurat (version 4.0.3). Cells with fewer than 500 detected genes and for which the total mitochondrial gene expression exceeded 20% were removed and mitochondrial genes and genes that were expressed in fewer than three cells were also removed by Roser et al. We used sctransform for the normalization with default parameters . Then peTo get the risk assessment criterion, the adult lung gene expression was taken from the 27 different adult tissues data and then merge with the gene expression of 6 fetal tissues data between 10th and 20th week of fetal development. In order to make the tissues comparable, we applied the quantile normalization  on the mThe R package WGCNA (version 1.70) was used to explore gene networks of fetal development gene expression data. Co-expressed genes were clustered into networks and created “modules,” which are defined as groups of highly interconnected genes. We use a soft threshold power of 12 for transforming the unsigned co-expression matrix based on the correlation between genes into an adjacent matrix. After module identification, phenotypic data (which tissue and development stage come from) were correlated with modules. We analyzed the correlation between eigengene with all genes in the brown module and the correlation between all genes in the module with the intestine tissue. Then, genes with high correlation coefficients were selected as hub genes. Gene Significance (GS) or Module Membership (MM) were calculated by correlating the gene’s expression with the respective phenotypic trait or the respective module’s expression, respectively.High relationship genes (genes with MM > 0.79 and GS > 0.24) in intestine vs. brown module were used for enrichment analysis using the R package clusterProfiler (version 3.18.1). Gene Ontology (GO) enrichment analysis was performed using the function enrichGO, and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was performed using the function enrichKEGG.As CMV and ZIKV were commonly studied that can be transmitted vertically and cause fetal complications, such as microcephaly, multiorgan disease, congenital malformations, and intrauterine growth restriction , so firsFurther, we investigated the cell types in the placenta which are possibly vulnerable to be infected by SARS-CoV-2 utilizing the single-cell sequencing (scRNA-Seq) data of maternal–fetal interface . FirstlyWe then investigated the distribution of ACE2 and TMPRSS2 in different cell types ,D. SimilWe next sought to find out the cell types in which the two cofactors were expressed simultaneously. The results  showed tThe expression levels of ACE2 and TMPRSS2 in 6 tissues  between 10th and 20th week of fetal development were investigated . We founNext, we studied the expression levels and changes of TMPRSS2 in these tissues during embryonic development . We notiTo further study the risk of SARS-CoV-2 infection in different fetal tissues and development stages, we established a risk assessment criterion. The expression levels of ACE2 and TMPRSS2 in adult lung and placental tissue were used as the baseline, and we classified the tissues’ intrusion risks into five levels: high, medium–high, medium, medium–low, and low . In our previous analysis, the intestine was at a high risk of being infected by SARS-CoV-2 during fetal development, so further we focused on the Brown module and sought to find out the hub gene set of it. It is found that ACE2 and TMPRSS2 were both hub genes in the Brown module, indicating that a group of genes with similar expression patterns as ACE2 and TMPRSS2 may influence the intestine organ development collectively  on the six fetal tissues during embryonic development stages. Results showed that totally 30 gene modules with similar gene expression patterns were identified , which wectively .Subsequently, we analyzed the function of hub genes in the Brown module and the biological pathways that they were involved in. These genes were significantly enriched in pathways associated with infection processes, providing further evidence that ACE2 and TMPRSS2 were co-expressed with genes associated with pathogen infection. KEGG analysis also suggested that hub genes may be related to intestinal pathogen infection pathways , and GO Since the outbreak of COVID-19, there have been many contradictions and controversies over whether SARS-CoV-2 can transmit through the placenta . There aFurther, ACE2 and TMPRSS2 were found to be co-expressed in VCT, a subtype of trophoblasts. Trophoblast is the major cell type of the placenta, and an important part of the maternal–fetal interface, that is the key basis of fetal development . There aSubsequently, our results showed that the abundance of ACE2 and TMPRSS2 was much higher in multiple embryonic tissues during different fetal development stages than in the placenta and gradually increased. In addition, estimated by our risk assessment criterion, stomach, and intestine were at a high or medium–high risk of SARS-CoV-2 infection. The results taken together suggested that SARS-CoV-2 may be transmitted from infected mothers to the fetus during the whole pregnancy and present adverse impact on multiple organs of the fetus, especially the digestive system. Though existing researches showed that most newborns delivered by COVID-19 pregnant women were asymptomatic, few with slight respiratory symptoms , there wMoreover, we found that ACE2 and TMPRSS2 were commonly enriched in intestinal immunity-related pathways and may involve in the biological processes related to infection and T-cell activation. Similarly, a recent study proposed that during pregnancy, maternally restricted infection can directly impose epigenetic changes on fetal intestinal epithelial stem cells, leading to long-lasting impacts on intestinal immune homeostasis . Furtherin vivo. In addition, the data are derived from physiological conditions of healthy people, but the infection of SARS-CoV-2 may affect the transcriptional profiles of the maternal–fetal interface and fetal tissues. Thus, the results should be interpreted with intense care and further clinical studies and confirmation experiments are necessary to get a more comprehensive conclusion.However, as a preliminary study, there are still some limitations in our study. First of all, all analyses are based on transcriptome data of various tissues and cells, which may not truly represent the overall state of protein expression At a time when global epidemic of COVID-19 is still serious, we call for enhanced maternal care throughout the whole pregnancy to prevent the potential impact and harm of SARS-CoV-2 maternal–fetal transmission. At the same time, more attention should be paid on relevant research, to explore the molecular mechanism of maternal–fetal transmission of the virus and provide guidance for clinical practice in the health of mothers and fetuses.The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/LZ designed the research. LZ and YL supervised this study and revised the manuscript. ZH and YW conducted programming. SM, CD, WC, and PY downloaded, managed, and processed the data. JL and SX searched for fetal development-related literatures. LQ provided guidance for the project. ZH and SX drafted the main manuscript text collectively. All authors contributed to the article and approved the submitted version.This research was funded by National Natural Science Foundation of China (31771459 and 82071657); and Guangdong Province (2021A1515010542). This research is supported by Pearl River S&T Nova Program of Guangzhou (201806010151), Guangdong Province Key Laboratory of Computational Science, and the Guangdong Province Computational Science Innovative Research Team (in part).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The novel severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), causing coronavirus disease-19 (COVID-19), has been responsible for approximately 75 million cases and 1.6 million deaths globally as of December 22, 2020. Currently, no treatment modalities or management options have been recommended by the National Institutes of Health (NIH) prior to patient hospitalization and supplemental oxygen requirement. This poses a unique challenge for outpatient primary care physicians, who are often tasked with initial care of patients early on in their disease course. During the pandemic, our family practice provided medical care to approximately 2,000 families located in the surrounding Brooklyn community. With only telemedicine at our disposal, our clinic was tasked with treating patients presenting remotely who may or may not have had COVID-19 - a large clinical diagnosis was made given the absence of in-person testing. Often co-administered, Azithromycin was considered a supportive agent that may or may not have increased the benefit of hydroxychloroquine. However, Azithromycin may perform well on its own for various reasons as it has been shown to have antiviral activity against other RNA viruses, anti-inflammatory properties, and antiviral effects within bronchial epithelial cells. Azithromycin has also shown efficacy as an add-on treatment for reducing asthma exacerbations - pertinent to the pro-inflammatory pulmonary conditions in COVID-19 progression - and may even prevent or treat bacterial co-infection in patients with SARS-COV-2.In order to investigate the association between Azithromycin and the COVID-19 disease process, our clinical study retrospectively identified patients who were prescribed Azithromycin (500 mg on day one + 250 mg on days two to five) during the peak months of the COVID-19 pandemic in New York City from March 2020 through May 2020. All patients prescribed Azithromycin with suspicion of COVID-19 infection were interviewed via telephone regarding their constellation of symptoms, compliance with the prescribed antibiotic for the intended course, symptom duration prior to and following antibiotic course initiation, as well as any further complications of their illness, if present. Ultimately, the majority of the patients who were interviewed over the phone concluded that a full course of Azithromycin helped improve their symptoms during their infection with COVID-19. Outcomes and complications in patients treated with Azithromycin were noteworthy in that there were no reports of pulmonary complications or deterioration of pulmonary function after treatment , although some patients did experience residual coughing and nasal discharge post-treatment. We believe further study of this treatment in the setting of experimental, randomized controlled trials may reveal the benefits of Azithromycin in terms of reducing infection severity, length, and limiting the incidence of complications in patients with COVID-19. The novel severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), causing coronavirus disease-19 (COVID-19), has been responsible for approximately 75 million cases and 1.6 million deaths globally as of December 22, 2020 . During It has been proposed that viral loads in COVID-19 patients are highest at the time of symptom onset and decline thereafter; thus, in the event that COVID-19 is suspected at first contact with a primary care physician, it may be beneficial to explore pharmacologic therapy for early management of COVID-19 ,7. SeverIn this observational study, we present the outcomes of patients with strong clinical suspicion of COVID-19 who presented to our family practice remotely for care. With no better treatment option available, patients were treated with Azithromycin, in addition to being given all recommended guidelines for self-isolation and testing, with strongly positive clinical responses and few complications.In order to investigate the association between Azithromycin and the COVID-19 disease process, our clinical study identified patients who were prescribed Azithromycin (500 mg on day one + 250 mg on days two to five) during the peak months of the COVID-19 pandemic in New York City from March 2020 through May 2020. Patient information was collected through NextGen Office, the electronic medical record (EMR) being used by our clinic. Inclusion criteria for patients comprised an electronic medical record (EMR) record of Azithromycin prescription between March 23, 2020 and May 31, 2020 (n = 39). Once patients who fit the inclusion criteria were compiled, additional information was gathered, including the date Azithromycin was prescribed, patient history of exposure to COVID-19, history of COVID-19 antibody test, history of COVID-19 antigen test, and history of COVID-19 symptoms . Once patient information was compiled, patients were contacted to follow up on their symptoms. All patients prescribed Azithromycin with clinical suspicion of COVID-19 infection were interviewed via telephone regarding their constellation of symptoms, compliance with the prescribed antibiotic for the intended course, symptom duration prior to and following antibiotic course initiation, as well as any further complications of their illness, if present. Patients who were included in the study were not prescribed any other medication alongside Azithromycin, other than non-steroidal anti-inflammatory drugs (NSAIDs) or acetaminophen as supportive therapies. During the initial encounter, all patients were advised to self-quarantine at home under suspicion of being contagious with COVID-19.Of the 39 patients who were prescribed Azithromycin, 18 had also tested positive for COVID-19 antibodies at a follow-up visit. We deemed these patients likely to be COVID-19 positive at their initial telehealth visit based on their clinical presentation and their subsequent antibody results, and grouped them together as Group A. Each of these patients were contacted individually and interviewed over the phone. Patients were asked a number of preset questions  against its drawbacks . Social distancing and supportive therapies aside, there were no other outpatient guidelines during the peak of the COVID-19 pandemic; thus, the encouraging history of Azithromycin use (as detailed previously) did not hold insignificant weight in treating our patients with no other recourse and worsening COVID-19 symptoms. Ultimately, the majority of the patients who were interviewed over the phone concluded that a full course of Azithromycin helped improve their symptoms during their infection with COVID-19. Outcomes and complications in patients treated with Azithromycin were noteworthy in that there were no reports of pulmonary complications or deterioration of pulmonary function after treatment , although some patients did experience residual coughing and nasal discharge post-treatment.While the authors do feel that, among our sample patient population, Azithromycin may have decreased the severity of COVID-19 symptoms and/or reduced the longevity of the disease process, this study does have several limitations to address. Our sample population does not have enough power to represent the entirety of New York City's COVID-19 patient population, as our clinic did not have the access to reach many numbers of patients during the pandemic. Further, this study does not demonstrate definitively that Azithromycin is an effective treatment for COVID-19 as the study is structured as an observational study and cannot determine causative relationships, only correlative ones. Finally, we cannot definitively claim that our patient sample did indeed have COVID-19 prior to being prescribed Azithromycin rather than afterward as we were unable to conduct COVID-19 tests on initial presentation due to pandemic restrictions. Our conclusions are thus based on strong clinical suspicion that patients presented with COVID-19 due to clinical presentation and COVID-19 antibody results upon follow-up.This observational study was conducted to demonstrate the efficacy of Azithromycin in treating COVID-19 from the outpatient perspective of a primary care provider. Especially when prescribed at the onset of patient symptoms, Azithromycin was well-tolerated, and the patients demonstrated improvement of symptoms within seven days. In many cases, Azithromycin use was even correlated with reversing the deterioration of patients who reported worsening of their symptoms in quarantine.Due to the novel nature of this pandemic, our reliance on telemedicine, and the observational, retrospective structure of this study, we acknowledge that our options for patient randomization, control groups, and blinding were limited. However, the patients we treated with Azithromycin reported no adverse effects, and there were no cases of decompensation or further deterioration in any of our patients. Thus, we believe our observations may be of use in opening doors for further discussion and potential use of Azithromycin in the outpatient setting during symptom onset in patients with suspected COVID-19 infection. We believe further study of this treatment in the setting of experimental, randomized controlled trials may reveal the benefits of Azithromycin in terms of reducing infection severity, length, and limiting the incidence of complications in patients with COVID-19.