Coverage evaluation surveys (CESs) are an important complement to routinely reported drug coverage estimates following mass drug administration for neglected tropical diseases (NTDs). Although the WHO recommends the routine use of CESs, they are rarely implemented. Reasons for this low uptake are multifaceted; one is uncertainty on the best sampling method. We conducted a multicountry study to compare the statistical characteristics, cost, time, and complexity of three commonly used CES sampling methods: the Expanded Program on Immunization’s (EPI’s) 30 × 7 cluster survey, a stratified design with systematic sampling within strata to enable lot quality assurance sampling (S-LQAS) decision rules, and probability sampling with segmentation (PSS). The three CES methods were used in Burkina Faso, Honduras, Malawi, and Uganda, and results were compared across the country sites. All three CES methods were found to be feasible. The S-LQAS approach took the least amount of time to complete and, consequently, was the least expensive; however, all three methods cost less than $5,000 per district. The PSS design resulted in an unbiased, equal-probability sample of the target populations. By contrast, the EPI approach had inherent bias related to the selection of households. Because of modifications needed to maintain feasibility, the S-LQAS method also resulted in a non-probability sample with less precision than the other two methods. Given the comparable cost and time of the three sampling methods and the statistical advantages of the PSS method, the PSS method was deemed to be the best for CESs in NTD programs. The metric for determining if MDA campaigns have met their target is drug coverage, defined as the number of individuals in the program area  who have swallowed the drug, or combination of drugs, divided by either the total population (“epidemiologic coverage”) or the population that was eligible to receive the drugs (“program coverage”). We know from experience and models that achieving high drug coverage, meaning coverage that meets or exceeds a disease-specific threshold set by the WHO, is expected to lead to the achievement of control and elimination goals.4The success of neglected tropical disease (NTD) programs working to control or eliminate disease depends on their ability to deliver preventative chemotherapy (PC) to populations at risk.5 A coverage evaluation survey (CES) is a valuable tool for evaluating program performance. Coverage evaluation surveys are population-based surveys designed to provide adequately precise estimates of treatment coverage that overcome many of the biases and errors that can undermine reported coverage. Whereas typically regarded as a tool for estimating treatment coverage, the benefits of and uses of CESs go beyond the estimation of treatment levels attained. Because participant recall in CESs has been shown to be generally accurate, particularly when surveys are conducted shortly after MDA, CESs can be used by country programs to assess the accuracy of the routine reporting system.6 Other potential uses for CESs include identifying reasons for noncompliance, detecting problems with the supply chain and distribution systems, measuring coverage in specific subpopulations of interest, and serving as a vehicle for estimating the value of other variables, such as those related to knowledge, attitudes, and perceptions regarding MDAs.Monitoring of PC coverage is typically based on reported coverage rates, which are calculated by aggregating drug distributors’ records of doses administered and dividing by a population estimate typically taken from census projections. Although reported coverage is an essential tool for program monitoring, it is prone to errors resulting from incorrect estimates of the target population, weak health information systems, and, at times, intentional inflation of the number of persons treated.8 Anecdotally, national NTD programs and implementing partners commonly mention as reasons for the infrequent use of CESs that they are expensive, resource intensive, and difficult to conduct well, and that the results arrive too late to impact the current MDA. When conducted, CESs have traditionally used a variation of the sampling design developed by the Expanded Program on Immunization (EPI) to measure immunization coverage.9 Indeed, the 2011 WHO manual on the epidemiological assessment of MDAs to eliminate lymphatic filariasis (LF) recommends a variation of the EPI approach for CESs.7 However, it has long been recognized that the original EPI cluster survey approach may lead to biased results because it does not rely on probability-based sampling.10 Whereas the EPI approach is fast and simple, survey statisticians have proposed a probability-based cluster sampling design in which primary sampling units (PSUs) are divided into segments as a way to reduce the workload, with the sample selected within a single segment. Another sampling alternative to the EPI approach that has been put forth is lot quality assurance sampling (LQAS), in which random or systematic sampling is used to determine if a threshold coverage level has been reached.11 Lot quality assurance sampling surveys are typically conducted in smaller strata , and then results from each stratum can be aggregated to calculate a coverage estimate for the entire survey area.13 The LQAS approach is touted for its small sample size, the ease of basing programmatic decisions on the threshold results, and the ability to gain programmatically useful information at the subdistrict level.The WHO recommends the routine use of CESs as a means of monitoring MDA programs, but they are rarely implemented on a routine basis.Until 2016, there was a lack of a single recommended sampling design for conducting CESs across the PC NTDs, which contributed to poor uptake of the surveys by country programs. As a result, the decision of whether to conduct a CES and the methodology used has been left to implementing partners and disease-specific focal points.In 2013, the Task Force for Global Health convened a stakeholders’ meeting on CESs to better understand the reasons for their infrequent use. A key output of the meeting was the need to conduct a rigorous comparison of the programmatic feasibility of the most common sampling methodologies, with the goal of developing a single set of guidelines for conducting CESs for PC NTDs.To address the stakeholder meeting recommendation, this multicountry study was designed to compare the cost, time, and complexity of CESs using the following sampling methods: the EPI approach, stratified survey using lot quality assurance sampling (S-LQAS) within strata, and probability sampling with segmentation (PSS). The three sampling methods were compared in Burkina Faso, Honduras, Malawi, and Uganda, always within the context of the ongoing NTD program. This article describes the sampling methods under comparison, interprets the resulting PC coverage estimates, compares the different feasibility metrics, and ultimately weighs the statistical properties and programmatic feasibility of each method to recommend the one best suited for NTD programs.The EPI, LQAS, and PSS methods were each piloted at the district level  in Burkina Faso, Honduras, Malawi, and Uganda . The fol15The PSU definition was consistent across all three sampling methods within each country and typically corresponded to the smallest administrative unit for which a population estimate could be obtained. Primary sampling units were typically villages, including localities and hamlets, or census enumeration areas (EAs). An EA is generally the area canvassed by a single census worker. The size of EAs in households at the time of the last census and EA maps are obtained from the country’s census office. Enumeration areas generally have fewer households and vary less in the number of households than other units used as PSUs, and have the desirable attributes for probability sampling described in the discussion section of this article. Because of these advantages, EAs are used as PSUs in Demographic and Health Surveys and in UNICEF’s Multiple-Indicator Cluster Surveys.Supplemental Table 1).The target population is defined as the population for which an estimate of PC coverage was desired. For CESs measuring MDA coverage for LF, onchocerciasis, or trachoma, the target population was everybody living in the targeted district, regardless of MDA eligibility. This aligns with the WHO identified targets for epidemiologic coverage  using total population as the measure of size. On arrival at each selected cluster, the survey team asked the local leaders to identify the center of the PSU. The starting household was chosen by picking a random direction from the center of the PSU by spinning a pen or bottle, enumerating all households in the chosen direction up to the outer border of the PSU, and then picking one at random to be the first selected house. Household sampling proceeded by selecting the nearest-neighbor household, defined as the household with a front door closest to the previously selected household. Within each selected household, all members of the target population were interviewed. This process continued until the target sample size for the cluster (the same for each cluster) was obtained. If the sample size was met before enrolling everyone in the final household, then enrollment continued until all household members were included.The EPI approach is a cluster sampling approach for calculating coverage that has been implemented thousands of times around the world.17 Generally, a small simple random sample is taken from a population (or “lot”), and the results are used to classify the lot as “acceptable” or “unacceptable” relative to a given threshold. With the lots treated as strata, prevalence estimates and standard error can then be calculated for the lots as a whole.Lot quality assurance sampling is a random sampling method that was originally developed by the manufacturing industry and later applied to public health.Districts selected for the stratified sample using LQAS within each stratum (the S-LQAS approach) were first divided into five supervisory areas (SAs) that corresponded to subdistrict areas of MDA supervisory responsibility. These SAs were the survey strata. First, 19 villages or EAs were selected systematically from within each SA using PPES sampling with the number of households as the measure of size. It was possible for a large village or EA to be selected more than once. Within each selected village or EA, a single household was chosen; two households were chosen if the village or EA was selected twice. Whenever possible, household selection was performed by picking a random number between one and the total number of houses in the village or health system register; the selected household was the one corresponding with the random number. When a register was unavailable, the survey team asked the village leaders to make a list of all households and randomly pick one. If a register was unavailable and the village/EA was too large for the village leader to enumerate, then the team first divided the PSUs into segments of approximately equal size in households, randomly selected one, and then enumerated all households in the selected segment and randomly selected one.To select a single respondent from the selected household, names of everyone living in the household, regardless of MDA eligibility, were listed on a piece of paper that was placed in a hat or bowl. One name was drawn, and that person was enrolled in the study. If the selected individual was not present, then another member of the household was asked to serve as a proxy respondent for the absent individual. In the event that a proxy was not present or if the selected household was empty, the nearest-neighbor household was visited and a single individual chosen for enrollment, as described earlier.19 First, the sampling team constructed a list of all PSUs in the survey area, each with its projected number of households. If PSU size in households was not already available, then it was calculated by dividing each PSU’s projected total population by the average household size. The estimated number of households in each PSU was then divided by 50 and rounded to the nearest integer to determine the number of 50-household segments to assign to each PSU. Next, 30 PSUs were selected from the list of all PSUs in the survey area by PPES sampling using the number of segments per PSU as its measure of size. On arrival at a selected PSU, the survey team worked with the local leaders to divide the PSU into a predetermined number of segments equal to the number of segments used for the PPES selection of the PSU. Segments within a PSU were delineated such that each had approximately the same number of households. One segment was selected at random, and a fixed proportion of households was selected systematically from among all households in the segment. The same proportion was used in all selected segments and was expected to produce the overall target sample size. All residents of the selected households were enrolled in the survey. If one or more residents of a selected household were not present at the time of the survey, then a family member was asked to serve as a proxy respondent and respond on their behalf. If no proxy was available, then the absent individual was excluded from the survey; there was no selection of make-up households because the sample size included inflation for nonresponse. The reason for defining PSU size as the number of 50 households it contains is based on field experience, indicating it would result in an efficient balance for NTD CESs between the time needed for segmentation (increased by segments with fewer households) and the time needed to enumerate and visit households within segments (increased by segments with more households). As shown by The PSS design produces an equal-probability sample of the target population and is derived from the “modified segment design” option described in the manuals for rounds 2–4 of UNICEF’s Multiple-Indicator Cluster Surveys and by Turner et al.f = sampling fraction of households, and r = anticipated rate of nonresponse.Within-segment sampling fraction of households :Probability of selection for a target population member living in the survey area:where PSU = primary sampling unit  and pop = population.P is the expected proportion of coverage , δ is the desired level of precision , and r is the anticipated nonresponse rate  and was calculated using the following formula, where design effect (DEFF) is the anticipated DEFF, nse rate .n= , while keeping the risk of both alpha and beta errors less than 10%. Results were aggregated across the SAs to calculate a weighted coverage estimate for the entire district, taking account of the stratified survey design. To achieve a coverage estimate with comparable precision (±5%) and confidence level (95%) to the EPI and PSS designs would have required visiting 384 separate villages/EAs per district, which was deemed infeasible. Instead, it was decided that (±10%) precision, at the same 95% CI, was acceptable and resulted in a feasible sample size of 96. This was reduced to 95 so that it resulted in an integer when divided by five (the number of SAs). Therefore, 19 people were selected in each SA  and wrongly classifying coverage as at or above a threshold when it is below the threshold (type II). A sample size of  each SA .https://osf.io/j9wgr/).To assist the survey teams with the sample size calculations and site selection, an Excel-based tool was developed that includes separate calculation sheets for each methodology  that had taken place 6 months before the assessment. The Ministry of Health formed three survey teams, each of which was trained on one of the sampling methods and assigned to a separate district. The EPI survey was implemented in Diebougou district, the S-LQAS survey in Dano district, and the PSS survey in Batie district. As per the study protocol, districts were selected to be as similar as possible with regard to population density, area size, and endemicity of NTDs. In addition to the standard CES questionnaire, the national NTD programs added questions to assess the population’s knowledge, attitudes, and perceptions related to the LF MDA.In Honduras, the CESs were conducted in June–July 2015 and were used to measure the deworming coverage  among preschool-aged children  1–2 months after the MDA. Five survey teams were formed: two teams jointly implemented the EPI approach in Gracias district, two teams jointly implemented the PSS approach in San Juan district, and one team implemented the S-LQAS in Lepaera district. These districts were selected based on the program need, safety for study teams, and similarity of demographic and epidemiologic characteristics. The Honduran program determined that ±10% precision was sufficient for all three sampling methods, resulting in a smaller sample size for the EPI and PSS surveys than the other countries. Furthermore, because the target population was only 24–59 months, The Malawi CESs were conducted in February of 2014 and were used to evaluate the coverage of an LF MDA  that had taken place 6 months prior. The districts of Machinga, Balaka, and Zomba were selected for the study, based on the needs of the program and the demographic and epidemiologic similarities of the districts. Three district-level teams were identified by the MOH and each trained on one of the sampling methods: the EPI method in Machinga district, the S-LQAS method in Balaka district, and the PSS method in Zomba district.In Uganda, the CESs were conducted in October–November 2014. To accommodate the National Program’s request to evaluate multiple drug packages, integrated CESs were conducted to measure the coverage for LF and onchocerciasis , distributed 6 months prior, as well as coverage for schistosomiasis and trachoma , distributed 4 months prior. Survey team members were trained on approaches to help improve participants’ ability to recall. Techniques included letting participants hold examples of each pill while describing the unique aspects of each MDA  and reminding participants which diseases each drug treats. Because Amuru district is considered a high-risk area for schistosomiasis, both children and adults were eligible to receive praziquantel. Consequently, everybody living in the district was considered part of the target population for the integrated CES. To obtain a more meaningful comparison of the relative feasibility of the sampling methods, the Ministry of Health decided to conduct all three sampling methods in the Amuru district. Three survey teams were formed at the national level and trained on all three methods. The teams then worked together to conduct three independent surveys in Amuru district, starting with the PSS sampling method, followed by the S-LQAS method and then the EPI method. As the selection of PSUs was performed independently for each sampling method, in some instances, the same PSU was included in more than one coverage survey and received multiple visits from the survey teams.Each survey team comprised one driver and two surveyors. One surveyor served as the record-keeper, in charge of recording the time of arrival and the survey responses in the handheld electronic device and one interviewer in charge of interviewing the respondents and showing examples of medication offered during the MDA. On arrival in a selected PSU, the survey team introduced themselves to the local leader and sought his or her permission to implement the CES. Once permission was granted, the survey team identified a local guide  to help navigate the PSU and introduce the survey team at the selected households.At each selected household, the survey team members introduced themselves to the head of household and sought verbal consent for each family member to participate in the survey. All members of the target population were considered eligible to participate in the survey. To increase participant recall, individuals were shown examples of the drug(s) that were offered during the MDA before being asked to respond to the survey questions. Caregivers were asked to respond on behalf of children aged < 10 years. If a respondent was missing but expected to return the same day, then the survey team returned later the same day. If the respondent was still missing at the second visit or missing and not expected to return at the time of the initial visit, then another adult in the household was invited to answer on behalf of the missing respondent. Such answers were noted as proxy responses in the database. In the event that no one was present at a selected household, the household was skipped, and the survey team proceeded to the next selected household.To measure the relative feasibility of each sampling methodology, the survey teams were asked to record the time of arrival and departure at each PSU. This information was validated against the automatic time and date stamps recorded by the cell phones at the initiation and completion of each survey record. At the end of the survey, the teams calculated the number of days it took to complete the survey fieldwork, the mean time (in minutes) to finish sampling within a PSU, and the cost of the survey. In addition, at the end of the CES, each team member was asked to complete a qualitative questionnaire to assess their feelings regarding the complexity, challenges, and overall impression of the sampling methodology to which they were assigned.20All data were collected using the LINKS system  on Android-based cell phones.Ethical clearance from the local institutional review boards was sought in advance of each study. In Burkina Faso, ethical clearance was granted from the Ethical Committee for Health Research in the Ministry of Health. In Honduras, ethical clearance was provided by the Pan American Health Organization’s Ethical Review Committee. In both Malawi and Uganda, the Ministries of Health considered the CES to be part of routine public health program practice and each sent a formal letter indicating that ethical approval was not necessary for the study. Permission to conduct the survey was obtained from community leaders on arrival in each PSU, and all participants gave verbal consent before participating in the survey.21 Confidence limits for the S-LQAS survey were calculated by treating the survey as a stratified sample. Data cleaning and basic analyses were performed in SAS v9.4 , whereas the complex survey analysis was conducted in R version 3.3.1  using the “survey” package.23Drug coverage was calculated as the number of people who reported having swallowed the drug(s) divided by everyone enumerated in the survey area (“epidemiologic coverage”). The one exception was for coverage of albendazole in Honduras, where the denominator was the number of PSAC in the survey area. For the S-LQAS survey, the SA coverage results were weighted according to the projected total population of each SA to arrive at the district-wide estimate. Confidence limits for the EPI and PSS methods were calculated using the paired selection model, described by Kish, which accounts for the implicit stratification that occurs when PSUs are selected from a geographically ordered sampling frame and for variance inflation due to the correlation of responses within each PSU.A total of 11,094 people were interviewed for the 12 independent coverage surveys, conducted across the four countries . The surIn Burkina Faso, the results from all three surveys indicate that MDA coverage exceeded the WHO target threshold for LF (surveyed coverage ≥ 65%). In Dano and Batie districts, the reported coverage fell within the 95% CI for the surveyed coverage, serving as a validation of the reported coverage and an indication that the reporting system is working well. In Diebougou district, the reported coverage narrowly exceeded the upper confidence limit of the coverage estimate by survey .The surveyed coverage estimates from Honduras indicate that none of the three district sites achieved the WHO target threshold of ≥ 75% coverage for soil-transmitted helminthiasis. In Lepaera district, the reported coverage (42%) was included within the CI around the coverage estimate by survey (33% and 54%), serving as validation of the reported coverage, whereas in Gracias and San Juan districts, the reported coverages of 89% and 76%, respectively, far exceeded the upper confidence limit around the coverage estimate by survey .In Malawi, the coverage estimates by survey for all three districts exceeded the WHO target threshold of ≥ 65% coverage for LF; however, only in Balaka district was the reported coverage also validated by the survey coverage results. In Machinga and Zomba districts, the reported coverage  exceeded the upper confidence limit around the coverage estimate by survey .Finally, in Uganda, the three sampling methods were used independently in the same district and separate estimates of coverage were obtained for each drug offered. All three sampling methods found that coverage for praziquantel and azithromycin was the lowest of the four drugs, and far below the MDA target thresholds of 75% and 80% for schistosomiasis and trachoma, respectively. Although the surveyed coverage estimates for albendazole and ivermectin were higher, they too fell short of the 65% target coverage by all three sampling methods. The reported coverage was universally high, relative to the surveyed coverage, for all four drugs; none of the three coverage sampling methods resulted in estimates that validated the reported coverage .In addition to the 2-sided 95% CIs around the survey coverage estimates, The results from the feasibility calculations are shown in Summary results from the qualitative questionnaire  suggest 28 and NTDs31; however, we are not aware of any studies that have also compared the feasibility of different coverage sampling methods in the context of NTD programs. This study was designed to compare the feasibility and statistical merits of three common coverage sampling methods  across a variety of country settings and disease platforms, with the aim of recommending a single CES sampling method for NTD programs to adopt moving forward.Coverage evaluation surveys are an important tool, used by public health programs to monitor the reach of an intervention. For NTD programs, CESs are essential for understanding the expected impact of MDAs, assessing the accuracy of the routine reporting system, and identifying ways to improve program performance. Because of the many sampling methods and adaptations that have been used for coverage surveys over the years, there have been several studies conducted to compare the coverage estimates and survey characteristics of different sampling methods for vaccination coverageAll three CES methods were found to be feasible, in the sense that they were successfully conducted by national NTD programs using local staff. Overall, the S-LQAS approach was the fastest method to complete, requiring one team on an average of 14 days to complete the survey in the field; consequently, it was also the least expensive. The PSS approach required the most time to complete sampling within a PSU; however, overall, the EPI and PSS approaches took the same amount of time to complete the full survey (19 days). A closer look at the variation in time to completion suggests that the differences may have more to do with the characteristics of the districts themselves than the sampling methodology. For example, in districts with lower population density, the surveys took longer and team members had to walk further to find the next household, regardless of the method used. The Uganda study was designed to provide the best comparison of feasibility across the three sampling methods ; however, it is hard to disentangle potential confounding due to the survey teams’ ability to adapt and improve over time. The teams reported that the work got easier and faster as they went on, with team members scoring the first approach (PSS) as the most difficult and the last approach (EPI) as the least difficult. For the field teams, the practical difference between the sampling methods relates mainly to the selection of the starting household within each PSU, the most time-consuming step. When asked to rank the difficulty of selecting the starting house, all three methods received scores ranging from “very easy” to “difficult,” with the PSS approach receiving the only “very difficult” score.32Although important, feasibility alone is not sufficient for identifying an optimal sampling method. The statistical qualities of the survey design merit careful consideration to ensure that the survey results are sufficiently accurate for program decision-making. The potential bias inherent in the EPI approach, whereby households have different but undefinable probabilities of selection, cannot be corrected for in the analysis. It is worth noting that because of this potential for bias, the EPI recently abandoned its classic 30 × 7 cluster methodology (the approach on which the “EPI” method described in this article is based) in favor of a more robust sampling method using segmentation.33 Although this design may be worth considering for future surveys, it was deemed impractical in this instance because the need to account for clustering in the analysis would make it hard to interpret the LQAS decision rules. As a consequence of selecting only one individual per household, individuals living in larger households had a lower probability of selection than those living in households with fewer residents. These unequal selection probabilities become a bias concern if household size is associated with MDA coverage.Stratified survey with lot quality assurance sampling can, in principle, result in an unbiased estimate of district coverage by combining results across the SAs, as long as every person in the survey sample has a known probability of selection. This could be achieved by recording the number of members in each selected household, randomly selecting one and then weighting that member’s response by the inverse of their selection probability. However, for the SA-level classifications to be valid, every individual must have an equal probability of selection. Selection probabilities would be equal if all members of a household were selected for the sample, as opposed to randomly selecting one person per household as was done in this study. Sampling 19 households, as opposed to 19 individuals, would constitute a “cluster LQAS” sampling design.It is also important to point out that the sample size used in this study for the S-LQAS design resulted in significantly less precision than the other two methods ; achieving comparable precision with the S-LQAS approach would require visiting 384 different PSUs. An important benefit of the S-LQAS design is the ability to classify coverage within an SA as above or below the target threshold within each survey area. Although insightful, because MDA decisions are often made on at a district level, this SA information did not change programmatic conclusions.Of the three sampling methods compared here, only the PSS method results in a probability sample and is the favored approach for conducting CESs. In addition to the benefits of unbiased sampling, because the PSS results in an equal-probability sample, the point estimate can be interpreted directly, without the need for weighting or statistical adjustments, a nontrivial advantage for country teams that often have limited access to statistical software. Although this method requires survey teams to segment each selected PSU, when asked to rank the difficulty of this task, most team members found segmentation “easy” to perform. Segmentation became increasingly difficult for the survey teams in more populous PSUs, which require dividing the PSU into a greater number of segments. One way to avoid this challenge is to use EAs as PSUs instead of villages. Enumeration areas have several advantages over villages as PSUs: they are jointly exhaustive and mutually exclusive ; they are relatively consistent in population size and generally have smaller populations than other units that have been used as PSUs; and they perform well in both urban and rural settings, and EA maps, often available now with GPS-defined borders, are typically available from the census office as well as spreadsheets with EA size in households at the time of the last census. Some country programs have reported difficulty in obtaining these documents from the census office; this may occur less frequently if the national EPI program, which has adopted a similar survey methodology, joins the NTD program in requesting them. Because the feasibility of the PSS approach is comparable to that of the other two methods considered here, its statistical advantages make it the preferred approach for conducting CESs.Although the PSS approach may be the favored method for CESs, it is important to note that even with some sampling biases, all three sampling methods provided useful information back to the programs. Not only did the surveys provide information on whether target thresholds were being met and if the routine coverage reporting system was working well but because they were supplemented with additional questions regarding knowledge, attitudes and practices, they also provided more detailed information that enabled the programs to diagnose where implementation challenges lie. For example, in Burkina Faso, the team learned that most survey respondents heard about the MDA from a town crier, as opposed to radio spots or posters. In Malawi, the team learned that MDA refusals were very rare and that most instances of no treatment were due to individuals being away from home at the time of MDA. The results from Uganda enabled the program to identify a critical but previously undetected problem with the supply chain system that resulted in too few drugs being allocated to the district. The challenges with the supply chain also explain the exceedingly high DEFF observed in Uganda , where c34 Recall reliability is of particular concern for integrated surveys, in which respondents are asked to differentially recall their ingestion of two or more drugs, or two or more interventions, potentially given at separate time points. Integrated surveys have the potential to conserve resources, minimize community interruption, and maximize the information gained. Whether for a single or integrated coverage survey, a best practice is to implement the CES as soon after the MDA as possible. Indeed, Budge et al.6 found that participant recall for triple drug MDA  was most accurate 1 month after MDA, but still relatively high 12 months post-MDA. When asking respondents to recall their participation in two or more campaigns, it is important that the survey teams are well trained in tactics that can help jog participants’ memories, such as showing examples of the different drugs, bringing a dose pole, and describing what the campaign team would have been wearing. The results presented here from Uganda suggest that participants differentially recalled their ingestion of albendazole and ivermectin, compared with azithromycin and praziquantel, which were given during two separate MDAs. These differential recall results were replicated across all three survey designs; because the three surveys took place in the same Ugandan district, this is good evidence of internal validity.A challenge and potential limitation of any CES is the accuracy of self-reporting. There is a dearth of literature recall reliability for NTDs, whereas the literature for caregiver recall in childhood vaccination surveys suggests that the figures can vary quite widely.35 Since the release of this recommendation, several tools have been created to assist NTD programs in the design, implementation, and analysis of CES using PSS. An Excel-based CES Sample Builder tool helps programs determine the appropriate sample size, select the PSU, and identify the number of segments required in each PSU; a manual and training materials describing how to conduct CESs have been created; and to assist in the analysis and interpretation of the CES results, a Web-based Coverage Survey Analysis tool was developed.37 More recently, a job aid was created by a team of experts, in consultation with the WHO, to help guide NTD programs in deciding when, where, and why to use CESs in the context of ongoing MDAs.38In 2016, on viewing the preliminary results from this study, the WHO Strategic and Technical Advisory Group for NTDs recommended that national NTD programs “implement CESs using PSS.”Coverage evaluation surveys are an essential tool in the monitoring and evaluation framework of NTD programs. The WHO has helped remove a barrier to the uptake of unbiased, statistically valid coverage evaluations by recommending a single, standardized method and providing resources and assistance to implementers. This study demonstrates that the PSS approach is feasible to implement, can be applied in a variety of country settings where the target population is spread out throughout the survey area, and a sampling frame exists with geographic units that can be used as PSUs and are accompanied by at least approximate estimates of total population or total households as a measure of size. Furthermore, the experience from Uganda and Honduras suggests that CESs can be used to conduct integrated monitoring across NTDs and other public health programs. By adopting the same sampling methodology as the immunization program, one can expect the familiarity with the PSS method and the number of survey teams trained in it to increase over time. The year 2020 is a pivotal year, with many program milestones being reevaluated and an increasing number of NTD programs performing at scale, CESs will remain an indispensable tool for monitoring the progress toward control and elimination goals and improving program effectiveness.Supplemental materials


Emergency physicians are responsible for assessing the severity of a patient’s burns, which determines whether the patient needs to be transferred to a burn center. Such a proper assessment represents a daunting task because severe burn injuries are rare. Inaccurate estimates often result in unjustified and costly transfers and unneeded fluid resuscitation and assisted ventilation procedures. Telemedicine offers a solution to these challenges. The present pilot study aims to investigate the feasibility, acceptability, and potential value of a large telemedicine initiative at the University of Montreal Health Center’s burn center and its network of referring hospitals.A three-stage study protocol is proposed to achieve this objective. First, a proof of concept phase will assess the technical feasibility of telemedicine at one referring hospital with a high volume of patient transfers. Second, the organizational and human feasibility of the project will be evaluated in four referring medical centers. All teleconsultation sessions will be analyzed using the WHO’s telemedicine implementation model. The third phase will consist of evaluating the potential impacts of telemedicine in a subset of 10 referring hospitals. The quality of communications between referring physicians and specialists will be assessed using semi-structured interviews. A pre-test/post-test with a comparison group design will be used to assess the effects of telemedicine on patient transfers, ventilation procedures, patient complications, mortality, length of ICU stay, and additional surgical procedures. The economic viability of telemedicine will be assessed using a cost-minimization approach.The telemedicine initiative is expected to yield positive and significant outcomes that are relevant to a wide range of medical centers that already use or are considering using a similar technology. The contribution of this pilot study lies in its ability to reveal technological, organizational, and human barriers and provide a preliminary assessment of the clinical and economic value of a large-scale telemedicine initiative in the context of burn medicine. Exposure to intense heat or harmful sources of electricity or chemicals can damage the skin and adjacent tissues. Severe burn injuries, which have historically been defined as > 20% of the total body surface area , can be Although various techniques can be used to assess burn area and depth , in pracIn order to address these challenges and streamline the process of patient transfer to the burn center, senior administrators at the University of Montreal Health Center  have decided to invest in a large-scale video-based telemedicine project. At this time, mobile phones are the predominant communication technology used by referring physicians and CHUM’s consulting specialists. Whereas the use of personal mobile devices may enrich communication between physicians and improve clinical decision making, it also raises several issues with regard to the security and confidentiality of medical information, the traceability of the discussions between providers, and the transfer and storage of medical notes and images in the electronic health record (EHR) system of the participating hospitals , 16.Non-compliance with the ethics rules of the Quebec College of Physicians. The College mentions the need to comply with practices set forth in An Act to establish a legal framework for information technology, particularly with respect to patient confidentiality and recordkeeping. This framework specifies that (a) images of a patient taken with a smartphone must be duly erased from the device after use; (b) transmission of patient information and data storage must be secure and confidential; and (c) the information sent  must be uploaded to the patient’s electronic medical record.Imprecise assessment of the body surface area affected. The analysis of the data in the SIRTQ database found differences of 10 to 45% in the estimates made of body surface area (2016 and 2017).Unjustified transfers of patients to the burn center. According to the medical specialists interviewed, a stay in the center of less than 24 h indicates an unjustified patient transfer. The rate of unjustified transfers was approximately 11% in 2016 and 12% in 2017.Unjustified use of assisted ventilation procedures. According to the medical specialists, withdrawal of assisted ventilation less than 24 h after transfer to the center indicates unjustified intubation and mechanically supported ventilation of the patient. The rate of unjustified ventilation from 2012 to 2017 was 39%.Expenses incurred for unjustified procedures. The actual cost associated with transferring a patient to the burn center plus 5 days of hospitalization is estimated at CA$13,330 (excluding fee-for-service expenses). An additional CA$10,540 must be added in cases of aeromedical evacuation (representing close to 2% of the transfers to the center). Patients transferred under assisted ventilation require assistance on the ambulance  in addition to the usual paramedics, resulting in higher costs.Our research team’s assistance was first requested to perform an independent, yet comprehensive assessment of existing practices and problems. To this end, we collected and then analyzed three data sources: (1) semi-structured interviews with two members of the burn center’s medical team and six referring physicians who had recently contacted the burn center; (2) data from Quebec’s trauma registry information system ; and (3) the burn center’s internal documents. Our analysis revealed five major problems with current work methods and tools:Next, our research team was asked to assess the feasibility, acceptability, and potential value of the telemedicine initiative. We developed a three-stage pilot study which we describe next. Our specific objectives are twofold: (1) to identify the technological, organizational, and human issues that are likely to surface before and during the deployment of telemedicine at the burn center and its referring hospitals; and (2) provide a preliminary, yet comprehensive assessment of the clinical and economic outcomes associated with the use of telemedicine in this context.CHUM is one of the largest medical centers in Canada. It is a public not-for-profit hospital whose primary mission is to provide inpatient and ambulatory care to its immediate urban clientele, as well as specialized and ultra-specialized services to the broader metropolitan and provincial population. The burn center at CHUM is one of the two referral centers for severe burn victims in Quebec, Canada  was selected for this purpose. This app, which has been certified by the Quebec’s health authorities for remote collaborative communications, is HIPAA compliant and incorporates innovative tools like augmented reality for remote virtual guidance, supervision, and training. It is deployed in over 80 countries to support remote wound care, tele-ultrasound, teleconsultations with patients, interactive tele-surgical assistance, and remote procedural supervision, among others. In the present telemedicine project, ReactsTM is to be used for secure file transfers, instant messaging, and video conference calls.CHUM’s senior administrators first instructed the center for optimizing network flows  to centralize and coordinate requests for complementary expertise and patient transfers to the burn unit. COFR operates like a call management center. It consists of a dozen nurse clinicians who systematize access to the hospital, support patient management, and forward requests for complementary expertise. COFR supports the needs of several departments, including critical care, vascular surgery, and addiction medicine. Then COFR was charged with governing physician discussions using a telemedicine mobile application. The ReactsAs shown in Table The first phase will consist of evaluating the project’s technical feasibility in terms of various operational issues, such as access to a wireless communications network (a mobile or Wi-Fi network) in the emergency room, the user-friendliness of the telemedicine app, and the fluidity of discussions between the referring physician, the medical specialist, and COFR staff. The participation of a referring hospital with a high volume of patient transfers will be required. Technological feasibility will be evaluated through an iterative process in which the new work process and tools will be tested and adjusted accordingly. Various technical tests  will be performed through observations of all communications. Following these tests, physicians and COFR staff will be interviewed to assess the new work process and methods as well as the telemedicine mobile app’s strengths and weaknesses.Once the technical issues are sorted out, the second phase will consist of evaluating the organizational and human feasibility of the project. To this end, the new workflow methods and tools will be deployed in four referring hospitals. During a 9-month period, referring physicians and medical specialists will discuss cases over the telemedicine platform. This material will enrich the discussions and reflections during the follow-up interviews to be conducted with all the participating physicians. The analysis grid used in this phase and phase 1 will be based on the World Health Organization’s telemedicine implementation model . Based oThe third phase will consist of evaluating, over a period of 12 months, the clinical and economic value of the telemedicine platform that will be deployed to a subset of 10 regional hospitals (out of 73 referring sites) in early 2021. As in the previous phase, after each telemedicine session, a follow-up interview will be conducted with the pair of physicians involved. Participants will be asked to comment on the quality of their discussions as well as the perceived effects of telemedicine on the quality of case-based discussions and clinical decisions as well as on knowledge transfer . Next, several variables will be extracted from the SIRTQ database: (a) the rate of unjustified transfers, (b) the rate of unjustified ventilations, and (c) estimation differences. The quantities of unjustified procedures  will be analyzed as annual proportions for all the referring hospitals involved. Other outcomes available in the burn center’s or the referring hospitals’ EHR systems will be collected and analyzed, including patient complications, mortality, length of ICU stay, additional surgical procedures, and time to transfer to the burn center. Given that telemedicine will be gradually deployed to the 10 participating referring sites in 2021, data for the years 2019 and 2020 will serve as the baseline (pre-deployment) and will be compared with data for the years 2022 and 2023 (post-deployment). It is worth noting that the other referral burn center in Quebec, which is part of the Laval University Health Center, and 10 of its referring hospitals will serve as a control group. Telemedicine is not available at this referral center, and there is no plan to deploy it prior to the end of the present study. Hence, it will be possible to use the same data periods in both medical units. Last, a preliminary assessment of the economic viability of telemedicine will also be conducted using a cost-minimization approach )The proposed study protocol has some limitations. First, it may not be possible to detect all the specific effects of COFR and the telemedicine app, as these interventions will be deployed concurrently. In response to the problems found during initial management, it has been decided to use a stay of less than 24 h as the threshold for determining an unjustified, unnecessary transfer of a burn patient. However, we are aware that the length of stay of a burn patient is often estimated based on a percentage of the total area affected , 38. MeaIn conclusion, the telemedicine initiative described here is expected to yield positive and significant results that are relevant to a wide range of medical centers that are already using or are considering deploying similar technologies. The dissemination of study results will also be relevant locally, knowing that the CHUM’s administration intends to deploy telemedicine in other types of inter-facility transfers . The contribution of this pilot study lies in its ability to reveal technological, human, and organizational challenges and provide a preliminary assessment of the clinical and economic value associated with telemedicine in the specific context of acute care for severe burn victims.Additional file 1. Details of the transfers to the Burn Victim Unit (year 2017). This file presents the distance from the Burn Victim Unit (km) and the number of patient transfers for each of the institutions included in the areas of Western Quebec in 2017.


The successful recruitment and retention of health professionals to rural and remote areas of Australia is a health policy priority. Nursing or allied health professional students’ learning placements in the Northern Territory (NT) of Australia, most of which is considered remote, may influence rural or remote work location decisions.The aim of this study is to determine where allied health professionals and nurses who have had a student placement in the NT of Australia end up practicing.This research is an observational cohort study, with data collection occurring at baseline and then repeated annually over 10 years . The baseline data collection includes a demographic profile of allied health and nursing students and their evaluations of their NT placements using a nationally consistent questionnaire . The Work Location Survey, which will be administered annually, will track work location and the influences on work location decisions.This study will generate unique data on the remote and rural work locations of nursing and allied health professional students who had a placement in the NT of Australia. It will be able to determine what are the most important characteristics of those who take up remote and rural employment, even if outside of the NT, and to identify barriers to remote employment.This study will add knowledge to the literature regarding rates of allied health and nursing professionals working in remote or rural settings following remote or rural learning placements. The results will be of interest to government and remote health workforce planners.Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12620000797976; https://www.anzctr.org.au/ACTRN12620000797976.aspxPRR1-10.2196/21832 The bulk of the literature regarding work location outcomes focuses on medical students, with most studies reporting that an “organised, well-funded, rural placement or rural clinical school program produced positive associations with increased rural intentions and actual graduate rural employment” . ConsideFlinders University in Adelaide, Australia, has a long history of delivering education and training to develop the Australian NT health workforce ,38. In 2This research is a 10-year tracking study of the work practice locations of all nursing and allied health students who complete an NT work-integrated learning placement. The study will also investigate the factors that contribute to the work location decisions of the participants and will determine if and how an NT placement influenced career decision making.The overarching research question for this study is as follows: Where do nursing and allied health professionals who have had a student placement in the NT end up practicing? The primary objective of this study is to identify the workplace locations, annually, of nursing and allied health students who completed an NT work-integrated learning placement; this will be conducted for 10 years postgraduation. The secondary objectives of this study are as follows: (1) investigate factors that contribute to work location decisions and (2) determine if and how an NT placement influenced career decisions.The research will use a pragmatist theoretical framework -41. ThisStudy participants will be students or graduates, over the age of 18 years, of an Australian allied health or nursing training program and will have undertaken an NT placement as a student. Their placement, including any assessment of competence, will be concluded by the time of participation. Individuals who were already employed as a nursing or allied health professional and undertaking a placement as part of a postgraduate qualification will be excluded.Framed by our pragmatist approach and as part of our due diligence around appropriate research designs, we considered using Australian Health Practitioner Regulation Agency (AHPRA) registration data rather than participant survey data. However, only about half of the professions of interest are registered through the AHPRA: Aboriginal and Torres Strait Islander Health Practitioner, Chinese medicine, chiropractic, dentistry, medical radiation, nursing and midwifery, occupational therapy, optometry, osteopathy, pharmacy, physiotherapy, podiatry, and psychology. Disciplines that are not registered include audiology, dietetics and nutrition, disability, exercise physiology, medical laboratory science, orthotics and prosthetics, paramedicine, social work, and speech pathology. Therefore, relying on AHPRA data to answer our primary question will not provide coverage of all the professions of interest.The research design relies on access to the contact details of health professional students known to have undertaken work-integrated learning placements in the NT from 2017 onward. Flinders NT holds a secure database with the contact details of the placement students. These details were obtained for the purpose of supporting the placement; however, students consent to the use of their information for educational research purposes, such as our standard quality-improvement Student Satisfaction Survey regarding placement. Access to the database will allow the researchers to recruit participants to the study by contacting current and former students and inviting them to participate in the research.Ethics approval was provided by the Flinders University Social and Behavioural Research Ethics Committee . This study was registered with the Australian New Zealand Clinical Trials Registry (ANZCTR) (ACTRN12620000797976).In 2017, Flinders NT supported 462 students on placement from more than 20 universities across Australia. The average response rate to the standard quality assurance Student Satisfaction Survey regarding placement is about 30%. Based on 450 students per year undertaking placements and a conservative 15% response rate in the first year from students in the first three cohorts, approximately 203 participants will be added in the first year. Each year, another 450 students will be added to the sampling pool; however, over a 10-year period, we assume that the response rate will decline logarithmically by 1% each year, so that in the tenth year the response rate will be 6%. This equates to a total possible pool of 5400 participants who will each be offered up to 10 surveys, depending on the year they commenced in the study; however, with the declining response rates, we anticipate a final sample of 3175.The recruitment process comprises an email invitation to participate. If a message bounces back from an email address, we will contact the participant seeking an email address via the last known telephone number in the database.The research is comprised of annual online surveys, or phone surveys at the participant’s request. Survey 1  is the first survey and is an evaluation of the student placement. The following year, Survey 2  is sent, which comprises a 10-minute online survey asking about current work location and work location history and includes several questions regarding the influences on work location decisions. All subsequent years will use Survey 2  to ask about work location and work location history, but this survey will not repeat the initial questions regarding demography and the NT placement.Participation is voluntary and former students can also opt out of receiving any further surveys. In order to maximize the response rate while avoiding harassment of potential participants, we will send an email invitation to complete the survey, followed by two reminders that also contain the survey link. The reminders will include an option to cease receiving communications from Flinders NT.We will also advertise the research on our social media sites  in order to maximize exposure of potential participants to the study. This advertising will not contain a link to the survey but will simply describe the study and invite potential former placement students to contact us if they have not received an email invitation to participate.To summarize, participants will be recruited in one of two ways, depending on their year of NT student placement:Cohorts 1 and 2, which include health professional students known to have undertaken a Flinders NT–supported work-integrated placement during 2017 or 2018, will be contacted via their last recorded email address or phone number and invited to participate.Cohorts 3 to 12, which include health professional students undertaking Flinders NT–supported work-integrated placements from January 2019 and onward, will be emailed an invitation to participate at the conclusion of their placement.Participants who complete Survey 1 will have their names placed in a random draw to win one of four vouchers valued at Aus $50 (US $38). Participants who complete Survey 2 will have their names placed in a random draw to win one of 10 vouchers valued at Aus $100 (US $76).In this study, the intervention is having undertaken a student placement in the NT of at least one week in length. As part of standard accreditation processes, university-level health professional courses are required to demonstrate graduate competence in the application of knowledge and skills to patients and consumers of health care. Workplace-based placements, sometimes known as work-integrated learning activities, are a cornerstone of the curriculum because the students are working in health care workplaces under the supervision of a qualified health professional, learning to deliver the graduate competencies of the profession ,44.The supervision requirements, length, curriculum, and assessment of student placements vary according to the needs of the specific profession . WhetherTo maximize participation in the study, we will use a set of effective cohort retention strategies tested in previous cohort studies . For exThe primary outcome of the study is the workplace location, assessed using the Modified Monash Model (MMM) , with MMBaseline data  will be collected following student placements and will include age, gender, degree program in which student is enrolled, length of placement, placement location, Indigenous status, NT residency, and rural origin.To clarify the representativeness of the sample participants who respond each year, we will compare the distribution of the responders with the nonresponders in terms of age, gender, profession, length of placement, and Indigenous status. Descriptive analysis of deidentified aggregated data is planned. This will include survey response rates; number of student placements by profession and location, using the MMM and not town location; length and number of placements; gender; rural origin; NT residency; and influences on placement. Changes in work location will be analyzed by location. Factors associated with remote work location  will be analyzed using logistic regression.This study will generate unique data on the remote and rural work locations of nursing and allied health professional students who will have had placements in the NT of Australia. It will be able to determine what are the most important characteristics of those who take up remote and rural employment, even if outside the NT, and identify barriers to remote employment.The question of how many allied health and nursing students, as well as their characteristics, who have had a remote student placement go on to work remotely is a gap in the literature on remote work locations, which more typically focuses on medical students and to a lesser extent on nursing students. Filling this gap is important, given the federal funding invested in the RHMT Expansion Program as a strategy to grow a local remote health workforce. Given the national policy priority to recruit and retain health professionals in remote and rural areas, new insights into strategies to achieve this are needed. It is recognized internationally that building a remote and rural health workforce is a common challenge .The analyses will be able to determine what are the most important characteristics of those who take up remote and rural employment, even if outside the NT, while adjusting for potential confounders, and will identify independent barriers to remote employment. A meta-synthesis of recruitment and retention of occupational therapists and physiotherapists in rural areas found that the availability of, and access to, practice supports; opportunities for professional growth; and an understanding of the context of rural practice were important . FurtherThe very low population density in the NT makes it a unique context to study remote health workforce issues. How the factors influencing the selection of remote health workplace locations compared to rural settings needs further study.Possible limitations of this study revolve around potential low participation rates, which could bias outcomes. Prompts, reminders, and acknowledgements  will assist, but it may be that those most interested in rural and remote work will respond and that those who either had a negative experience of remote work while on placement or in some other context will choose not to participate. General information provided to the wider pool of nursing and allied health professional students about the study and the importance and benefits of rural and remote work will encourage participation in the study and will, more generally, promote interest in placements in the NT.


An increase in physical activity (PA) level is associated with reduction in chronic diseases. However, the number of older adults who meet the PA guideline is low and decreases with age. Bodywise is a free program that aims to promote healthy behavior and to encourage older adults who live in Washington, DC to adopt a healthy habit by increasing their PA. The Bodywise program offers water aerobics, yoga, low-impact aerobics, and chair exercise classes, conducted by trained instructors at the University of the District of Columbia. This study reports an evaluation of the implementation of this program based on the surveys completed by participants after finishing the classes. Participants were DC residents aged 60 or older. According to the surveys, 68% of participants have adopted one or more healthy habits since joining the Bodywise program. In addition, more than 62% of participants have an increase in awareness of healthy behavior through this program. Overall satisfaction with the Bodywise program is 93%, satisfaction with the variety of classes offered is 72% and satisfaction with offered skill levels is 75%. Furthermore, 81% of participants reported overall satisfaction with their instructor, specifically 100% satisfaction related to their knowledge and skill level, and appropriateness of selected music, moves, and exercises. In conclusion, the Bodywise program leads to an overall change in both awareness of healthy behavior and development of healthy habits in participants. Further research can investigate the correlation of health awareness and healthy habits with overall satisfaction with the program and the instructor.


Membrane technologies are nowadays widely used; especially various types of filtration or reverse osmosis in households, desalination plants, pharmaceutical applications etc. Facing water pollution, they are also applied to eliminate emerging contaminants from water. Incomplete knowledge directs the composition of membranes towards more and more dense materials known for their higher selectivity compared to porous constituents. This paper evaluates advantages and disadvantages of well-known membrane materials that separate on the basis of particle size, usually exposed to a large amount of water, versus dense hydrophobic membranes with target transport of emerging contaminants through a selective barrier. In addition, the authors present several membrane processes employing the second type of membrane. Emerging contaminants (ECs) are once again raising the question of water quality ,5,6,7,8 Notwithstanding the fact of dealing with sometimes hard to measure soluble amounts in water, Membrane filtration; specially NF and RO due to very small pores (<2 nm).Granular and powdered activated carbon adsorption for rapid filters and seasonal uses.Advanced oxidation processes recommended as extra treatments especially for drinking water quality improvement.Yang et al.  presenteGraphene and graphene oxide adsorption due to their high and functionalized surface areas.Adsorption on carbon nanotubes with high adsorption performance and physicochemical properties (despite high costs).Biological degradation, the most used technique, requires space and time but is energy efficient.Wang et al.  mentioneConstructed wetlands gathering a combination of natural processes: sedimentation, microbial hydrolysis and photolysis degradation ,26,27.Metal organic framework adsorption (relatively new technology) .Some alternative methods may be added:Moringa olifeira seeds [The number of sorbents used is still increasing ,32,33,34ra seeds . New metra seeds ,41,42,432 and H2O . AOPs and advanced catalytic oxidations are a very complex group of processes including ozonation, Fenton and foto-Fenton reaction, sonolysis, catalytic wet air oxidation processes, combined AOPs etc. [All of these methods have advantages and disadvantages. For example, advanced oxidation processes (AOPs), which are generally considered to be the most effective and universal, employ oxygen or free radicals to initiate the oxidation of undesired compounds ,45. The OPs etc. ,50,51,52OPs etc.  have a hMembrane technology suitable for ECs is problematic because of the diverse physicochemical properties of materials and the wide range of parameters to combine for separation enhancement. Different kinds of membranes, namely polymeric, hybrid, inorganic or supported, implement almost any material or chemical that may be required for testing. For example, coating allows modification of the membrane surface, applying a molecular layer in order to change surface characteristics of the membrane . ApproprThe presented paper focuses on membrane technologies. Certain are nowadays used widely to produce clean water (see next part Membranes for water treatment). The advantage is low saturation of the selective barrier compared to sorbets, as well as decomposition that can take place separately from treated water. The membranes’ function in eliminating ECs from water, usually exposes membranes to a large amount of water that passes through the selective barriers. These classical membranes aim at adequate performance, in terms of rejection, basing the separation mostly on size of the pores. That becomes highly challenging taking in consideration the large diversity of very small ECs. Albert Einstein said: “The world as we have created it is a process of our thinking. It cannot be changed without changing our thinking.” This paper tries to offer unusual, stimulating discussion about different kinds of dense membranes for removal of ECs, confronting the pore size mechanism model with the solution-diffusion model.The membrane processes listed in Certainly, it is easier to transport only one compound, e.g., water, through the membrane than diverse ECs. The most employed processes, e.g., NF, RO or FO, are supposed to retain contaminants and let the water pass through the selective barrier. Besides Donnan and adsorption, the separation is based mainly on a spherical exclusion mechanism ,73. AlthCharge of the moleculeHydrophobicity of the separated moleculeSize of the separated moleculeThe factors influencing the membrane selectivity, mentioned in reviews dealing with membrane separation and ECs ,91, are:Two properties describe the affinity of the molecule to the membrane, which indicate if the molecule is able to diffuse through the membrane or is able to penetrate its pores. The solvent is the permeating species, because of its small molecule size, in the most employed processes such as NF, RO or FO.Rejection of nonionic hydrophilic ECs  is a result of physical sieving.Rejection of hydrophobic nonionic ECs  is most influenced by the initial adsorption of the molecules on the membrane and, as the membrane gets saturated by the solute, the rejection decreases.Positively charged ECs  and negatively charged  rejection is connected with the electrostatic interactions between the molecule and the membrane surface, and with sieving.A detailed study discussing the factors influencing forward osmosis applied in the removal of ECs was presented by Coday et al. . Their wConsidering that the membranes used for osmosis and RO are rather hydrophilic, the message received is not clear: hydrophobic compounds can adsorb on a hydrophilic membrane and saturate it, increasing its hydrophobicity and its permeability for the hydrophobic compounds. This was observed and described in detail by Nghiem et al. , who proAcero et al. presented very interesting results illustrating how complicated the situation of the interaction between the separated substance and membrane can be. They used UF membranes with a large molecular weight cut-off (2000 kDa and more) and tested them with a water solution of hydroxybiphenyl. The molecular weight of hydroxybiphenyl is 170 g/mol and it should completely pass through the membrane’s pores if size exclusion was the only mechanism of rejection. However, the rejection of hydroxybiphenyl was nearly 100% because it was completely adsorbed on the membrane. This was proven also by a sorption experiment .Sometimes, authors themselves are confused by their own results. Radjenovic et al.  presenteStudies on the role of the surface charge of the membrane were presented by Bellona and Drewes as well as by Childress and Elimelech in their much-cited works ,92. ChilChange of the surface charge .Change of the hydrophobicity of the membrane.Adsorption of some trace contaminant in the foulant.Change of the roughness of the membrane surface.Unfortunately, all the mentioned interactions might be affected by membrane fouling in both the positive and negative senses. Studies connected with membrane fouling and its effect on separation have been published by numerous authors ,93,94,95Nghiem et al.  worked oAny possibility of worsening the quality of feed water influences the effectiveness of membrane separation. An example is the V&A Waterfront desalination plant, installed as part of Day Zero emergency measures in Cape Town. Notwithstanding the capability of producing 2 ML of potable water per day, its production is still struggling with poorer feed water quality than was originally expected. The selectivity of the membranes turns out to be insufficient because of unexpected pollutants in the feed. These are withdrawn by a huge stream of water, resulting in unsatisfactory quality of the drinking water produced .From the viewpoint of environmental impact assessment, NF and RO show weaknesses in assessing different parameters like global warming potential, nutrient enrichment, fossil fuel usage, ozone depletion or toxicity . NF requConsidering all the factors influencing membrane selectivity, hydrophobic dense membranes (with target affinities to ECs) could solve the problem of complicated interactions and fouling, with no necessity to push a massive amount of wastewater through the membranes by high-pressure pumps. Despite having many other benefits, there is almost no use of such membrane processes in water depollution from ECs. The authors are unable to say whether this is because the most employed processes, like NF, RO or FO, are automatically tested for ECs elimination, or because obstacles exist that have not yet been overcome; no such publication has been found on the subject. The evaluation of advantages and disadvantages of well-known membrane materials that separate on the basis of particle size, versus dense hydrophobic membranes with target transport of emerging contaminants through a selective barrier, will be presented in next paragraph.The composition of membranes in WT dealing with ECs is heading towards more and more dense materials . Dense membranes are known for their higher selectivity compared to porous constituents. Their transport process can be described as a solution-diffusion model. Still, even dense RO membranes provide separation based on pore size. Avoiding the permeation of water through the membrane and enhancing the transport of ECs may be achieved by using hydrophobic dense membranes. The authors simplify, in Note (a–c) Membrane separation based on pore size are the most employed membrane processes in WT such as UF, NF or RO. The processes are well described, membranes are available and the separation is fast. These processes were, however, not primarily designed for removal of ECs. There are several new studies trying to clarify whether UF, NF and RO may be successfully applied in removal of ECs. The rejection of different ECs by NF and RO were from 40 to 100% [ to 100% ,61,74,77Note (d) The advantage of classical processes, with separation based on pore size, is that only one membrane type is needed for treatment of all contaminants, but insufficient selectivity would lead to additional separation parts. Using dense polymeric membranes for target transport of ECs, several different types would be needed.Note (e) Whether the molecule of EC is retained by the RO or NF membrane depends on the characteristics of the molecule, namely its charge, hydrophobicity and size. Which molecules will be retained, and which not, cannot be well predicted because it is not only a matter of sieving . Example: “The molecular weight of the Hydroxybiphenyl is 170 g/mol and it should completely pass through the membrane’s pores if the size exclusion was the only mechanism of rejection. However, the rejection of Hydroxybiphenyl was nearly 100% because it was completely adsorbed on the membrane” [embrane” . Dense pNote (f) After treatment by RO we get nearly UP water and brine full of different ECs compounds. Such water cannot be released to the environment or drunk [or drunk . It mustNote (g) Membrane separation based on pore size suffers by fouling that can influence the interactions between the molecule and the membrane and, consequently, also the quality of rejection [ejection ; see alsThe removal of ECs by processes using dense membranes deserves attention of researchers. On one hand, classical technologies, e.g., RO, are commercially ahead and adapting for ECs removal. On the other hand, the membrane processes that may be potentially used for target transport of ECs (applying hydrophobic nonporous membranes), are not yet widely known for such treatment. Still, they are already recognized in other fields such as pervaporation (PV), membrane extraction and petraction, which is a special case of dialysis that uses the nonporous membranes.PV is a method for the separation of liquids through a membrane that is in contact with a liquid mixture on the feed side while a vacuum is applied on the permeate side. A phase change of the permeating component occurs as a result of such operation conditions. It enters the membrane as a liquid and leaves the membrane as vapor. The vapor is then usually trapped by refrigeration. Pervaporation processes are widely used for compound separation, especially in aroma and flavors extraction ,109,110,R, of the component i by the membrane is defined as the fraction of solute kept at the feed side regardless of membrane area or compound concentration. This factor shows a general rejection of the membrane toward the compound at a specific time t of the separation. Plotting rejection ratio as a function of time visualizes the breakthrough moment of the membrane [Cp,i,t and Cf,i,t0 are the concentrations of the compound i on the permeate side at the moment t, and initial concentration of the feed side, respectively.The rejection ratio, membrane .(1)Ri,tJ of the component i through a dense membrane (Equation (2)) is defined as the amount of the permeating substance related to the membrane area (A) per unit of time (t) [The permeation flux time (t) ,118:(2)J(1)Membrane thickness.(2)Driving force.(3)Permeability of the membrane.The permeation flux is influenced by:The influence of the membrane thickness is easy to understand, the thicker the membrane the lower the permeation flux. Driving force and permeability are more complicated.S of the component in the membrane and the diffusion coefficient (diffusivity) D of the component in the membrane:Permeability (Equation (3)) is the value that describes the affinity of the membrane material to the permeating component, and vice versa. In the case of the solution diffusion transport mechanism, it is usually defined as a product of the solubility (sorption) coefficient The solubility and diffusivity of the component in the membrane are easily measurable values but they are hard to predict. They are determined by certain interactions and similarities between the membrane and the permeating components, as discussed earlier.ix is the molar fraction of the component in the liquid phase, iγ is the activity coefficient of the component in the solution and isatp is the saturated vapor pressure of the component.The last thing that influences the PV flux of the permeating component is the driving force. Generally, the driving force is defined as the difference of the chemical potential of the particular component across the membrane. In the case of PV, the chemical potential difference is transformed into the difference between the fugacity of the permeating component in the liquid on the feed side of the membrane (Equation (4)) and the fugacity of its vapor on the permeate side of the membrane in the gaseous phase (Equation (5)).l is the membrane thickness [The permeation flux is then expressed as:hickness ,118.As mentioned in the introduction, ECs are a huge group of substances of different kinds. 2 and the membrane thickness was 2 µm. Because of the low vapor pressure of DBCP, the authors decided to heat the membrane to 150 °C to enhance the pervaporation flux. They presented the values of pervaporation flux calculated from the difference between the initial concentration of the DBCP in the feed and the concentration after the pervaporation experiment. They did not say whether anything was found in the cold trap after the PV. The concentration of the DBCP decreased after 10 hours of PV from 10 ppm to 2 ppm, but this could have been caused by the sorption of the DCBP in the membrane only, without passing through, because of the very low concentration of the substance studied. This conclusion is supported by the fact that the same group of authors, one year later, presented work dealing only with the selective sorption of emerging contaminants by a PDMS membrane from water and human milk, where DCBP was one of the studied compounds [There have been trials utilizing the pervaporation process for the removal of ECs from water. Higuchi et al. tried to use PV to remove 1,2-dibromo-3-chloropropane (DBCP) from water with a PDMS membrane . The autompounds . Higuchiompounds  also triPV is thus able to separate lighter and more volatile ECs from water. However, it is not suitable for less or nonvolatile ECs, yet, the process is suitable where separation is difficult and other membrane processes are insufficient.Pertraction is a membrane process using dense or liquid membranes, and the principles are similar to PV. The main difference is that there is liquid on both sides of the membrane: the donor, feed solution on one side and the acceptor solution on the other side. The driving force is also the chemical potential difference, but here it is transformed into the difference of the activity of the particular component across the membrane or, in the simplest case, the difference in the concentration of the permeating component At laboratory scale, pertraction is often performed as a batch process that causes a continual decrease of the driving force until the concentrations on both sides of the membrane are equal. A low concentration of ECs will worsen it. This can be solved by using a sweep liquid, which should be recycled in the process . Perfect stirring is necessary to keep both solutions homogeneous and thus the driving force maximal, and to avoid concentration polarization on both sides of the membrane.The word pertraction in connection with the separation of pharmaceuticals, ECs, endocrine disruptors etc., is hard to find. But inspiration can be drawn from studies on transdermal permeation of drugs. Such tests are performed with Franz diffusion cells and use thin dense membranes like silicone. Waters et al.  tested tA slight terminological diversity occurred during the review process about the interaction of the selected substances of interest . ContempIn general, pertraction can be highly selective and thus may not lead to losses of, for example, some important ions from water.Membrane extraction was developed and tested for analytics. The aim is to increase the concentration of an analyte in a sample by moving it from a worse solvent to a better one. It allows a transfer of the analyte from one solvent to another, avoiding mixing of the two solvents by dividing them with a nonporous membrane. In this case, the molecule is transported to the membrane in the donor phase mainly by convection , then the molecule is dissolved in the membrane. It diffuses through the membrane and dissolves in the second solvent. This solvent can be easily selected using solubility or partition coefficient data. Considering the batch mode of the separation, the process can be described as follows.iwS is the sorption coefficient of the separated component from the aqueous phase, which is a measurable value.ioS is the sorption coefficient of the separated component in the organic phase.The membrane flux is given by Fick’s law: The fact that there are different solvents on both sides of the membrane is reflected also in the mathematical description of the process, because of the different sorption coefficients. It is essential to know both sorption coefficients because this influences strongly the driving force of diffusion and they cannot be hidden in some overall mass transfer coefficient as in PV and pertraction. The factors leading to successful separation are the same as in previous cases: reasonable diffusivity of the component through the membrane and good affinity of the component to the membrane material. Enhancement of the separation here is provided by the better solvent used as an acceptor phase.Swelling of the membrane in the organic solvent may play an important role in this process. Swelling causes the membrane thickness to increase but also increases the diffusivity of the component in the membrane because the polymeric chains in the membrane material recede from each other. In addition, the organic solvent gets closer to the separated component during swelling.The solubility of many ECs in other solvents is several orders of magnitude higher than in water.To illustrate the difference between the solubility of ECs in water and in, for example, ethanol, a simple mathematical exercise may be done. The concentrations of ibuprofen and ethinyl estradiol in two particular studies from the Czech Republic were taken and it was calculated how much of the studied water could be theoretically extracted with 1L of Ethanol. The results are presented in Membrane-assisted extraction is usually mentioned in connection with the analysis of trace compounds in water or environmental samples ,131,132.A very complex and comprehensive review was presented by Hylton and Mitra . This puMembrane extraction with nonporous polymeric membrane into some convenient solvent could, therefore, be another possible method for removal of ECs from water. Membrane materials such as ordinary LDPE or silicone rubber may be effective enough. The solvent would have to be continually regenerated during the process. On the other hand, only a small amount of solvent (compared to the volume of the feed phase) would be necessary. The advantages and disadvantages are similar to previous alternatives, eliminating ECs from water though membranes. The process would be rather slow, requiring a long contact time and large membrane area. That would be the price for aiming for the highest selectivity and avoiding leakage linked to the immense water flux through a membrane. In addition, the membrane would not be exposed to high pressures. Last, but not least, the target compounds may be removed from the water without losing valuable ions.The authors fully agree with Taheran et al. that any method which only creates a more or less concentrated stream, including the membrane separations, cannot be used solely. Still, the popularity of membrane processes in water depollution is great, especially those with elevated water flux through the membranes. This paper compared and discussed a classical pore size mechanism approach of popular nondense (porous) or quasi-dense hydrophilic membranes versus real-dense membranes without pores. It underlines the advantage of, for example, RO being commercially ahead, notwithstanding new adaptation for ECs removal. On the other hand, it confirms beyond doubt that using real-porous membranes for the separation of hydrophobic components from water works, and is used widely, but in another field than suggested here.Use of real-dense membranes is proposed by the authors as a perspective way to reach the highest selectivity in elimination of ECs elimination. Such membranes are more suitable for flux of ECs through the membrane instead of water Therefore, a hydrophobic separation material would be preferred. Their limitation will surely be connected to the driving force. However, they offer better water/target compounds selectivity than any membrane separating principally on size of the pores . In addition, pressurizing the feed stream would not be necessary. The membranes could be suitable for purposes where high quality takes priority over large quantities. Target transport through the membrane can be suitable for each kind of EC, namely nonionic hydrophilic, nonionic hydrophobic, positively or negatively charged ECs. The real-dense membrane can be well programed for any group of ECs or a specific compound. Knowing the physicochemical properties of the membrane and the separated molecules, appropriate membranes may be employed and allow the emerging contaminants to be concentrated for the next step: safe degradation out of the treated water. The amount of eliminated ECs is not limited as in the case of sorbents. Moreover, concentrating the ECs might help to analyze their composition in water by means of common measurements, which are insufficient when the concentration is too low. As for convenient processes, PV may be used for more volatile compounds, and pertraction and membrane extraction for all ECs.