Incidence of Severe Acute Malnutrition After Treatment: A Prospective Matched Cohort Study in Sokoto, Nigeria 2018-2019 - Nigeria

Abstract
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Background
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Acute malnutrition is an important concern for children aged under 5 years, both globally and in Nigeria. Since the 2000s and the advent of Ready-to-Use Therapeutic Foods (RUTF), Severe Acute Malnutrition (SAM) has been commonly addressed through the WHO-recommended approach of Community-based Management of Acute Malnutrition (CMAM). CMAM programs provide treatment for children aged 6-59 months through an outpatient therapeutic program (OTP) service for uncomplicated cases and an inpatient service for complicated cases.

In Nigeria, children are admitted and discharged from the CMAM program using mid-upper arm circumference (MUAC) as the main criterion. Children with a MUAC <115 mm and no apparent health complications are admitted into the OTP.

CMAM is evidently effective in resolving SAM. However, evidence exists that children who have gone through an episode of SAM remain at higher risk of morbidity and mortality than children who have not. The evidence on SAM relapse is sparse with a high variation in estimates in the literature due to both contextual and methodological differences. This makes it difficult to understand the persistent risk of a SAM episode after initial recovery from the CMAM program, as well as the associated risk factors. Another important gap in the literature is the absence of comparison groups, making it difficult to determine the excess risk for SAM associated with a recent SAM episode.

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Research objectives
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The primary objective of this study was to assess the persistent and excess risk of SAM among children treated by the CMAM program.
· The persistent risk was assessed by measuring the 6-month incidence rate of relapse into SAM among children discharged as cured from the OTP services of the CMAM program.
· Excess risk was assessed by comparing this rate of relapse to the 6-month incidence rate of SAM in a cohort of community controls.
Our secondary objective was to identify factors that are associated with the risk of relapse.

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Methods
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We conducted a prospective matched cohort study that tracked 553 children who were discharged as cured from OTP and 526 community control children in Sokoto State, Northern Nigeria. Data were collected from September 2018 to May 2019. OTP-cured children were recruited from the health facilities at discharge from OTP. Control children were recruited in the same communities the OTP-cured children lived in. Outcomes and potential risk factors were measured in up to 12 fortnightly home visits, i.e. in a period of up to six months for each child.

This cohort study was implemented in several phases that took place sequentially, and that included recruitment of OTP-cured children, recruitment of community control children, first home visit (to collect baseline characteristics), and subsequent follow-up home visits. At each phase, different questionnaires were administered.

Geographic coverage
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This study took place in five rural local government areas (LGAs) in Sokoto State in Northern Nigeria.

Analysis unit
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- Households
- Individuals
- Children
- Health facilities

Kind of data
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Sample survey data [ssd]

Sampling procedure
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Selection of LGAs and health facilities
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This prospective matched cohort study was conducted in five rural local government areas (LGAs) in Sokoto State, northern Nigeria. Nine out of the 23 LGAs in Sokoto State hosted the CMAM program. Of these, four were excluded because they were either hosting another study looking at improving CMAM delivery, were peri-urban, or not easily accessible. In the selected five LGAs, the CMAM program had been running since 2010 and was being implemented throughout the study period. Within each LGA, five health facilities were hosting the CMAM program, and the study covered this exhaustive list of 25 health facilities (i.e. there was no sampling of health facilities within LGAs, all health facilities that were hosting the CMAM program in each LGA were included in the study).

Selection of children
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The study followed two cohorts of subjects:
1. First, a cohort of children who were i) admitted into OTP and discharged alive and as cured (children are discharged as cured from OTP if their MUAC is superior or equal to 115mm, and there are no signs of bilateral pitting oedema), ii) were aged 6-59 months at admission into the OTP, iii) had not previously been admitted to the OTP or inpatient care, and iv) whose households resided in the catchment area of the selected health facilities and were not planning to move out. These children are referred to as 'OTP-cured children.'
2. Second, a cohort of children i) from the same communities as OTP-cured children who had ii) no history of SAM or treatment for SAM, iii) no anthropometric or clinical signs of MAM (MUAC <125 mm) or of severe stunting (height/length-for-age z-score (HAZ/LAZ) <-3 SD) at the time of recruitment into the study, and iv) who were matched to the OTP-cured children based on a set of criteria. Each community control child was matched to an OTP-cured child based on the following criteria: i) residence (living in the same community), ii) age in months (being of similar age, and allowing up to 3-month difference), iii) sex (having same sex), iv) age of the mother (below or above 20 years of age), and v) level of education of the mother (no education, completed primary, and completed secondary or above). These children are referred to as 'community control children.'

Exclusion criteria for both cohorts of children for enrolment into the study included:
· Presence of disability or any congenital disease (after clinical examination) that affects growth or prevents accurate anthropometric measurement and/or prevents the child from eating normally;
· A sibling already enrolled into the study;
· The biological mother of the child having passed away; or
· Having a mother <15 years old.

Note that children were not sampled. Rather:
1. All OTP-cured children and their caregivers were approached to be included in the study as they were being discharged from the CMAM programme (during our recruitment period) and assessed for eligibility until a maximum number of participants was recruited.
2. Community control children were purposively recruited into the study within the communities of each OTP-cured child using a snowball approach.

Sample size (intended)
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The sample size determination was based on the relapse rate as the principal outcome variable.

The minimum sample size required for this study was calculated to be 500 OTP-cured and 500 community control children across the 25 facilities. This sample size would allow us to detect a 4% point difference in SAM incidence between both cohorts of children with 95% confidence. Calculation parameters were chosen conservatively and assumed an incidence of SAM among community controls of 1%, a total number of 25 clusters (health facilities), a coefficient of variation of cluster sizes of 0.9, and an intra-cluster correlation of 0.02. Sample size calculations were implemented using the clustersampsi tool in Stata.

With an anticipated loss to follow-up of 20%, the study therefore aimed to recruit 600 children per cohort.

Representativeness
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It is important to emphasise that the two cohorts of children included in this study are not necessarily representative of the overall population of children in Northern Nigeria or even Sokoto State. On the one hand, children from the OTP-cured cohort were recruited from health facilities in a purposefully selected set of LGAs within that state. Given the way that they were recruited, they do represent a census of OTP-cured children from those health facilities that were discharged as cured during the recruitment phase of this study and that were eligible for the study. However, the level of representativeness beyond that group is unclear. Community control children, on the other hand, were selected using snowball sampling, which essentially implies purposeful sampling within visited communities. Hence, generalising findings beyond the two groups covered in the study should only be done with care.

Mode of data collection
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Computer Assisted Personal Interview [capi]

Research instrument
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1. COHORT TIMELINE
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This cohort study was implemented in several phases that took place sequentially, and that included recruitment of OTP-cured children, recruitment of community control children, first home visit (to collect baseline characteristics), and subsequent follow-up home visits. At each phase, different questionnaires were administered.

At each health facility, a CMAM day is held once a week, rotating through all facilities per LGA so that no two facilities within an LGA have a CMAM day on the same day per week. Children who are enrolled in the CMAM programme and their caregivers attend CMAM days for check-ups and treatment. This study recruited OTP-cured children at these CMAM days, identifying children who were discharged as cured.

The data collection timeline was as follows:

1. OTP-cured children were recruited at health facilities on a rolling basis between September and November 2018. There, the study team screened all children who had been discharged as cured on that day for eligibility and consent to participate in the study. This meant enrolling children as they were successfully discharged from the CMAM programme in the 25 health facilities that formed part of this study. At each CMAM day and health facility, teams of two interviewers were present throughout the day to ensure that all children discharged from the programme on that day were screened for possible enrolment into the study and recruited if eligible up until the minimum sample size is reached.

2. Following recruitment into the study, each OTP-cured child was tracked to their community and visited at their home within 2 to 3 weeks of their initial recruitment. Field teams used the information collected at recruitment to locate children in their community. Most communities were accessed either on foot or by motorcycle. This constituted the first home visit where a long baseline questionnaire was administered.

3. Immediately after the first home visit of each OTP-cured child, a search for a suitable community control for that child was conducted. For each OTP-cured child, potential community controls were identified using a snowball approach. In essence, this approach meant that interviewers were referred to potential community control children by the mother of the OTP-cured child. Potential community controls were assessed with respect to their eligibility to enter the study and to whether they matched the corresponding OTP-cured child on a set of criteria (mentioned in the sampling section). The first community control to meet both sets of criteria was recruited into the study and the search for a community control for a given OTP-cured child ended at that stage. Once a control child was identified, the same first home (baseline) questionnaire was administered to the household and mother of that child.

4. Afterwards, both cohorts were followed-up fortnightly for a total of 12 home visits (the 12 visits includes the first baseline home visit).

5. Participation in the study for both cohorts ended at the 12th home visit, unless a child developed SAM earlier or dropped out of the study (e.g. family no longer consented to participate in the study or moved out of the community, or child had died), whichever came first. In total, children were followed up for a duration of up to six months after discharge from OTP. Within the six months of follow-up, if children were identified as being SAM by the field team, they proceeded to exit the study and interviewers referred those children to CMAM services.

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2. DESCRIPTION OF QUESTIONNAIRES
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There were a number of questionnaires that were used for this study.

During recruitment of OTP-cured children at the health facility
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A recruitment questionnaire for OTP-cured children was administered to the mother of the child on the day children were discharged and recruited into the study. This questionnaire assessed eligibility of the child and collected some information to help with locating the home of the child.

Additionally, data on children's health status at admission and discharge from the OTP were also collected from registration and treatment tracking cards kept at the facility by staff (OTP cards and Ration cards). This data was scanned on enumerator's tablets and later on entered into a database by data entry staff. Information that was entered from these records included anthropometric measurements and morbidity at admission, duration of treatment and anthropometric measurements at each visit to the OTP. Note that data from the scanned OTP and Ration cards has not been uploaded for public use due to data quality concerns. The data suffers from many missing observations, given that this data was not directly collected by the enumerators but relied on health facility staff filling in the OTP and Ration cards for the treated children.

During this phase, a health facility questionnaire was also administered in each health facility to assess adherence of the health facility to the Nigeria CMAM national guidelines and availability of OTP-related drugs and equipment and the general quality of infrastructure and resources. The survey also collected data on shocks that affected the catchment area of facilities in the year prior to the survey, such as drought, floods, sandstorms, and security-related events. In each health facility, this survey was administered once, on the first day the interview team visited the health facility. The survey used direct observation as well as interviews with the head of the health facility and the CMAM focal person in charge. If either of these individuals were not available on the day, other knowledgeable health facility member was asked to respond to the questions.

During recruitment of community control children
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A recruitment questionnaire for community control children was administered to the mothers of the children to assess eligibility and matching criteria and decide if they can be recruited.

During the first home visit
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At the first home visit, a long baseline questionnaire was administered to the mother of the recruited child and the household head to collect baseline information across several domains related to the child, mother, and household. Children's MUAC was measured using the WHO/UNICEF-recommended MUAC tape and measurement protocol, whereas height and length were measured with a precision of 0.1 cm, using boards manufactured by SECA: standing boards for children who were able to stand and lying-down boards for children unable to. The domains included in the baseline questionnaire include:
- Child level: height/length, mid-upper arm circumference; demographics; breastfeeding history; co-morbidities in the 2 weeks prior to the survey; immunization status; dietary diversity (24 hours prior to survey).
- Mother level: demographics; economic activity and education status; knowledge on child feeding and health-seeking behaviour; reproductive history and care; perceived OTP experience; networks in community.
- Household level: household demographics and composition; economic activity and education of household head; household assets and wealth; water, sanitation, and hygiene infrastructure; household food security and dietary diversity; deaths in the household in the year prior to the survey.

During the follow-up home visits
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At each follow-up home visit, a short follow-up questionnaire was administered to the mother of the child to collect child-level co-morbidity data in the 2 weeks preceding the visit (a subset of the questions asked in the baseline questionnaire) and to measure the child's MUAC.

In the final follow-up visit (i.e. the visit when the child exited the study either because they developed SAM or if they reached the final 12th visit), additional questions were asked of the household including on mother's employment status, changes in the breastfeeding and pregnancy status of mothers, deaths in the household, household food security, child feeding, household and child dietary diversity, and mother's feeding knowledge and practices. These questions were a subset of those asked in the baseline questionnaire and they were added in order to understand if household, mother, or child conditions assessed at the first home visit might have changed at the point of exit. Note that these additional questions were not asked of children who dropped out of the study (because the interviewers would not have known that the previous visit was going to be the final exit visit).

All questionnaires were administered using the Computer-Assisted Personal Interviewing software CSPro (Version 7.1.3), and OTP and Ration cards were scanned and data entered digitally using the SurveyCTO software. Questionnaires were translated into Hausa and administered to all respondents in Hausa.

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3. NOTE ON THE DEFINITION OF SAM
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SAM was determined using the WHO and national MUAC criteria of MUAC <115 mm. Given that this study's objective was to identify definite relapses and cases of SAM that would require treatment, we classify a child as having SAM if his/her MUAC =112 mm at any home visit or if his/her MUAC is between 112 and 115mm for two consecutive visits. The reason we do this is to account for the possibility of measurement error, i.e. it is difficult to identify whether children around the 115mm MUAC cut-off temporarily dip into SAM or whether they are a certain SAM case that requires treatment.

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4. NOTES ON THE DATA COLLECTION THAT MIGHT BE RELEVANT FOR DATA ANALYSIS
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Survival analysis techniques can be used to analyse the data.

An important point to emphasise is that for OTP-cured children there was a lag of up to three weeks between their recruitment at the health facility and the first visit at home (where we collected baseline data). Some children had already relapsed into SAM at the first home visit before additional data on these children could be collected. For those children who relapsed between recruitment and the first home visit, it would therefore not be possible to assess whether certain time-varying characteristics collected at the first home visit - e.g. child-level health indicators - materialised as a consequence of relapse or prior to relapse. This is a limitation and could present implications for data analysis, depending on the type of analysis the users of the data wish to conduct. Specifically, it is important for the analysis not to suffer from endogeneity if for instance users are interested in assessing the effect of certain factors on relapse rates. There are options to deal with this limitation, for instance, i) limiting the analysis to the factors/covariates that could reasonably be assumed to be time-invariant between recruitment and the first home visit, or ii) defining the time origin for OTP-cured children as the first home visit (as opposed to their recruitment from the health facility) and restricting the analysis to the subsample of children that had not relapsed into SAM at the first home visit (though this option would entail a significant reduction in sample size).

Cleaning operations
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Given the data was electronically collected, it was continually checked, edited and processed throughout the survey cycle.

A first stage of data checking was done by the survey team which involved
(i) checking of all IDs;
(ii) checking for missing observations;
(iii) checking for missing item responses where none should be missing; and
(iv) first round of checks for inadmissible/out of range and inconsistent values.

Additional data processing activities were performed at the end of data collection in order to transform the collected cleaned data into a format that is ready for analysis. The aim of these activities was to produce reliable, consistent and fully-documented datasets that can be analysed throughout the survey and archived at the end in such a way that they can be used by other data users well into the future. Data processing activities involved:

- Reshaping datasets in order to produce data files for each unit of observation,
- Anonymising data by removing all variables that identify respondents such as names, address, GPS coordinates, etc.,
- Classifying non-response and coding them using a pre-determined classification scheme,
- Reviewing 'Other (specify)' responses by checking if any of the responses fall into existing response categories and can be recoded into the existing category or if there are multiple similar other responses that warrant the creation of a new response category (a decision to be made by the data analysts), and
- Properly naming and labelling the variables in each dataset.

The datasets were then sent to the analysis team where they were subjected to a second set of checking and cleaning activities. This included checking for out of range responses and inadmissible values not captured by the filters built into the CAPI software or the initial data checking process by the survey team.

A comprehensive data checking and analysis system was created including a logical folder structure, the development of a detailed data analysis guide and template syntax files (in Stata), to ensure data checking and cleaning activities were recorded and that all analysts used the same file and variable naming conventions appropriately.

Response rate
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- Out of a total of 645 OTP-cured children that were recruited into the study, 553 were found at the first home visit and deemed eligible, 83 were not found and 9 were later discovered to not be eligible.
- Out of a total of 543 community children that were recruited into the study (met eligibility criteria and were matched to OTP-cured children) at the first home visit, 17 were discovered later on to not have been eligible (and therefore were dropped).

Therefore, the sample size of the study (and consequently the number of observations of the published data) consists of 553 OTP-cured children and 526 community control children.

In terms of the outcomes of children at the end of the study:
- Of the 553 OTP-cured children, 378 did not experience SAM during the study period and therefore lasted until the 12th home visit; 134 experienced SAM during one of the visits (at which point their inclusion in further follow-up visits ended); 32 dropped out of the study at some point (3 withdrew their consent later, and 29 were no longer traceable); and 9 died during the study period (at which point their inclusion in further follow-up visits ended).
- Of the 526 community control children, 488 did not experience SAM during the study period and therefore lasted until the 12th home visit; 3 experienced SAM during one of the visits (at which point their inclusion in further follow-up visits ended); 30 dropped out of the study at some point (6 withdrew their consent later, and 24 were no longer traceable); and 5 died during the study period (at which point their inclusion in further follow-up visits ended).

摘要
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背景
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急性营养不良是全球及尼日利亚5岁以下儿童的重要健康问题。自2000年代以来，随着易于使用治疗食品（RUTF）的出现，严重急性营养不良（SAM）通常通过世界卫生组织（WHO）推荐的基于社区的急性营养不良管理（CMAM）方法进行治疗。CMAM项目为6至59个月的儿童提供治疗，通过门诊治疗计划（OTP）服务治疗简单病例，以及住院服务治疗复杂病例。
在尼日利亚，儿童通过使用上臂围（MUAC）作为主要标准被纳入和出院。MUAC小于115毫米且没有明显健康并发症的儿童被纳入OTP。
CMAM在解决SAM方面显然是有效的。然而，有证据表明，经历过SAM事件的儿童在发病率和死亡率方面仍然高于没有经历过SAM事件的儿童。关于SAM复发的研究证据很少，文献中估计值差异很大，这可能是由于背景和方法差异造成的。这使得难以理解在CMAM项目初步恢复后，SAM事件的持续风险以及相关的风险因素。文献中的另一个重要空白是缺乏对照组，这使得难以确定与最近SAM事件相关的超额风险。
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研究目标
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本研究的主要目标是评估通过CMAM项目治疗的儿童中SAM的持续和超额风险。
· 通过测量从OTP服务中治愈出院的儿童中6个月复发到SAM的发病率来评估持续风险。
· 通过将此复发率与社区对照组中6个月SAM的发病率进行比较来评估超额风险。
我们的次要目标是确定与复发风险相关的因素。
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方法
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我们在尼日利亚北部索科托州的索科托州进行了553名从OTP治愈出院的儿童和526名社区对照儿童的队列研究。数据收集时间为2018年9月至2019年5月。OTP治愈的儿童在从OTP出院时被招募。对照组儿童在OTP治愈儿童所在的同一社区被招募。对每个儿童进行了多达12次为期两周的居家访问，即每个儿童为期六个月的期间。
本研究分阶段实施，包括OTP治愈儿童的招募、社区对照儿童的招募、首次居家访问（收集基线特征）和后续的随访居家访问。在每个阶段，都进行了不同的问卷调查。
地理覆盖范围
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本研究在尼日利亚北部索科托州的五个农村地方政府（LGA）进行。
分析单位
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- 家庭
- 个人
- 儿童
- 健康设施
数据类型
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样本调查数据 [ssd]
抽样程序
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地方政府和卫生设施的选择
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在尼日利亚北部索科托州的五个农村地方政府（LGA）进行了这项前瞻性匹配队列研究。索科托州共有23个地方政府，其中9个设有CMAM项目。其中，有4个被排除在外，因为它们正在举办另一项旨在改进CMAM交付的研究，是近郊地区，或者不易到达。在选定的五个LGA中，CMAM项目自2010年起一直在运行，并在整个研究期间实施。在每个LGA内，有五个卫生设施提供CMAM项目，研究涵盖了每个LGA中提供CMAM项目的所有25个卫生设施（即LGA内没有对卫生设施进行抽样，每个LGA中提供CMAM项目的所有卫生设施都被纳入了研究）。
儿童的选择
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本研究遵循了两个受试者队列：
1. 首先，一个队列包括以下儿童：i）被纳入OTP并出院时存活且被治愈（如果儿童MUAC高于或等于115mm，且没有明显的双侧凹陷性水肿迹象，则从OTP出院时被治愈），ii）在OTP入院时年龄为6至59个月，iii）以前没有被纳入OTP或住院治疗，iv）其家庭居住在所选卫生设施的服务区域，且不打算搬出。这些儿童被称为‘OTP治愈儿童’。
2. 其次，一个队列包括来自与OTP治愈儿童同一社区的儿童，这些儿童：i）没有SAM病史或SAM治疗史，ii）在招募进入研究时没有MAM（MUAC <125mm）或严重矮小（身高/年龄z得分（HAZ/LAZ）<-3SD）的体格测量或临床体征，iii）根据一组标准与OTP治愈儿童相匹配。每个社区对照儿童根据以下标准与一个OTP治愈儿童相匹配：i）居住地（生活在同一社区），ii）月龄（年龄相似，允许有3个月的差异），iii）性别（具有相同的性别），iv）母亲的年龄（低于或高于20岁），v）母亲的受教育程度（无教育，完成小学，完成中学或以上）。这些儿童被称为‘社区对照儿童’。
两个队列儿童纳入研究的排除标准包括：
· 存在影响生长或阻碍准确体格测量的残疾或任何先天性疾病（经临床检查后）；
· 已有兄弟姐妹被纳入研究；
· 儿童的亲生母亲已去世；或
· 母亲年龄小于15岁。
请注意，儿童没有进行抽样。相反：
1. 所有OTP治愈儿童及其照顾者都在从CMAM项目（在我们的招募期间）出院时被纳入研究，并评估其资格，直到招募到最大数量的参与者。
2. 社区对照儿童在每个OTP治愈儿童的社区内被有目的地招募到研究中。这是通过滚雪球方法实现的。换句话说，这种方法意味着调查员由OTP治愈儿童的母亲推荐潜在的社区对照儿童。根据抽样部分的描述，对潜在的社区对照儿童进行评估，以确定其是否有资格进入研究，以及他们是否与相应的OTP治愈儿童在一系列标准上相匹配。符合这两套标准的第一个社区对照儿童被纳入研究，为给定的OTP治愈儿童寻找社区对照儿童的过程就此结束。
样本量（预期）
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样本量确定基于复发率作为主要结果变量。
本研究所需的最低样本量为500名OTP治愈儿童和500名社区对照儿童，跨越25个设施。此样本量将使我们能够检测两个队列儿童之间SAM发病率的4个百分点差异，置信度为95%。计算参数被保守地选择，并假设社区对照儿童中SAM的发病率为1%，总共有25个集群（卫生设施），集群规模的变异系数为0.9，集群内相关系数为0.02。样本量计算使用Stata中的clustersampsi工具进行。
预计20%的随访丢失，因此，本研究旨在每个队列招募600名儿童。
代表性
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重要的是强调，本研究中包含的两个儿童队列并不一定代表尼日利亚北部或索科托州的总体儿童人口。一方面，OTP治愈队列的儿童是从该州有目的地选定的LGA内的卫生设施中招募的。鉴于他们的招募方式，他们确实代表了在招募阶段从这些卫生设施中治愈出院且符合研究资格的OTP治愈儿童的普查。然而，超出该群体之外的代表水平尚不清楚。另一方面，社区对照儿童是通过滚雪球抽样选择的，这本质上意味着在访问的社区中进行有目的的抽样。因此，只能在谨慎的情况下将研究结果推广到研究涵盖的两个群体之外。
数据收集方式
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计算机辅助个人访谈 [capi]
研究工具
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1. 队列时间表
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本研究分阶段实施，包括招募OTP治愈儿童、招募社区对照儿童、首次居家访问（收集基线特征）和后续的随访居家访问。在每个阶段，都进行了不同的问卷调查。
在每个卫生设施，每周举行一次CMAM日，每个LGA的所有设施轮流进行，以便LGA内的任何两个设施在每周的同一天都没有CMAM日。参加CMAM项目的儿童及其照顾者参加CMAM日进行检查和治疗。本研究在CMAM日和卫生设施中招募OTP治愈儿童，识别被治愈出院的儿童。
数据收集时间表如下：
1. OTP治愈儿童在2018年9月至11月期间滚动招募。在那里，研究团队筛查了那天被治愈出院的所有儿童，以确定其资格和同意参与研究。这意味着在25个构成本研究一部分的卫生设施中，儿童在成功从CMAM项目中出院时被纳入研究。在每次CMAM日和卫生设施中，两组成员在当天全天都存在，以确保当天从项目中出院的所有儿童都被筛查以确定其可能的招募资格，并在达到最低样本量之前被招募。
2. 在被招募进入研究后，每个OTP治愈儿童都被追踪到其社区，并在其首次招募后的2至3周内在其家中进行访问。现场团队使用招募时收集的信息来确定儿童在社区中的位置。大多数社区要么步行到达，要么骑摩托车到达。这构成了第一次居家访问，在那里进行了长期基线问卷。
3. 在每个OTP治愈儿童的首次居家访问后，为该儿童寻找合适的社区对照儿童。对于每个OTP治愈儿童，使用滚雪球方法确定了潜在的社区对照儿童。基本上，这种方法意味着调查员由OTP治愈儿童的母亲推荐潜在的社区对照儿童。根据抽样部分的描述，对潜在的社区对照儿童进行评估，以确定其是否有资格进入研究，以及他们是否与相应的OTP治愈儿童在一系列标准上相匹配。第一个符合这两套标准的社区对照儿童被纳入研究，为给定的OTP治愈儿童寻找社区对照儿童的过程就此结束。一旦确定了对照儿童，就对那个儿童的家庭和母亲进行了相同的第一次（基线）问卷。
4. 之后，两个队列都进行了每两周一次的随访，总共12次居家访问（包括第一次基线居家访问）。
5. 两个队列的参与在第12次随访结束时结束，除非儿童在之前发展为SAM或退出研究（例如，家庭不再同意参与研究或搬出社区，或儿童死亡），以先发生者为准。总共，儿童在从OTP出院后的6个月内进行了随访。在随访的6个月内，如果儿童被现场团队确定为SAM，则退出研究，调查员将那些儿童推荐到CMAM服务。
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2. 问卷描述
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在这次研究中使用了多个问卷。
在卫生设施中招募OTP治愈儿童时
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对OTP治愈儿童的母亲在儿童出院和招募进入研究的那天进行了招募问卷。该问卷评估了儿童的资格并收集了一些信息，以帮助确定儿童的家庭地址。
此外，从卫生设施工作人员保存在设施中的登记和治疗方案卡（OTP卡和配给卡）中收集了儿童在入院和从OTP出院时的健康状况数据。这些数据由调查员扫描并随后由数据录入人员输入数据库。从这些记录中输入的信息包括体格测量和入院时的发病率，以及每次访问OTP时的治疗时间和体格测量。请注意，由于这些数据不是由调查员直接收集的，而是依赖于卫生设施工作人员为接受治疗的儿童填写OTP和配给卡，因此数据存在许多缺失观察值。
在此阶段，还向每个卫生设施进行了卫生设施问卷，以评估卫生设施对尼日利亚CMAM国家指南的遵守情况，以及OTP相关药物和设备的可用性，以及基础设施和资源的总体质量。该调查还收集了在调查前一年影响设施服务区域的冲击数据，例如干旱、洪水、沙尘暴和与安全有关的事件。在每个卫生设施中，该调查在采访团队首次访问卫生设施的第一天进行。该调查使用直接观察以及与卫生设施负责人和CMAM负责人进行的访谈。如果这两个人在当天不可用，其他了解情况的卫生设施成员将被要求回答问题。
在招募社区对照儿童时
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对社区对照儿童的母亲进行了招募问卷，以评估资格和匹配标准，并确定他们是否可以招募。
在首次居家访问时
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在首次居家访问时，对招募儿童的母亲和家庭负责人进行了长期基线问卷，以收集与儿童、母亲和家庭相关的多个领域的基线信息。使用世界卫生组织/联合国儿童基金会（WHO/UNICEF）推荐的MUAC带和测量协议测量儿童的MUAC，而身高和长度使用精度为0.1厘米的SECA制造的板进行测量，对于能够站立的孩子使用站立板，对于不能站立的孩子使用躺下板。基线问卷中包含的领域包括：
- 儿童层面：身高/长度，上臂围；人口统计；母乳喂养史；在调查前两周的共病；免疫接种状况；膳食多样性（调查前24小时）。
- 母亲层面：人口统计；经济活动和教育状况；对儿童喂养和健康寻求行为的认识；生殖史和护理；对OTP体验的认识；社区网络。
- 家庭层面：家庭人口统计和构成；家庭负责人经济活动和教育状况；家庭资产和财富；水、卫生和卫生基础设施；家庭粮食安全和膳食多样性；在调查前一年家庭中的死亡。
在随访居家访问时
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在每次随访居家访问时，对儿童的母亲的短期随访问卷进行了调查，以收集在访问前两周的儿童共病数据（基线问卷中询问的问题的子集）并测量儿童的MUAC。
在最后一次随访访问（即儿童退出研究是因为他们发展为SAM或达到了最后的第12次访问）时，向家庭提出了额外的问题，包括关于母亲的就业状况、母亲母乳喂养和怀孕状况的变化、家庭中的死亡、家庭粮食安全、儿童喂养、家庭和儿童膳食多样性以及母亲的喂养知识和实践。这些问题是基线问卷中询问的问题的子集，它们被添加进来，以便了解在首次居家访问时评估的家庭、母亲或儿童状况是否在退出点发生了变化。请注意，这些额外的问题没有询问退出研究的儿童（因为调查员不知道上一次访问将是最后的退出访问）。
所有问卷都是使用计算机辅助个人访谈软件CSPro（版本7.1.3）进行的，OTP和配给卡被扫描并以数字方式输入，使用SurveyCTO软件。问卷被翻译成豪萨语，并使用豪萨语对所有受访者进行问卷调查。
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3. SAM定义的说明
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SAM是根据世界卫生组织和国家MUAC标准确定的，即MUAC <115毫米。鉴于本研究的目标是确定确切的复发和需要治疗的SAM病例，如果儿童在任何居家访问时的MUAC等于112毫米或连续两次访问时的MUAC在112毫米和115毫米之间，则将其归类为SAM。我们这样做是为了考虑到测量误差的可能性，即难以确定围绕115毫米MUAC截止点的儿童是否暂时下降到SAM或是否是确实需要治疗的SAM病例。
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4. 可能与数据分析相关的数据收集说明
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可以使用生存分析技术来分析数据。

一个重要的问题是，对于OTP治愈儿童，从在卫生设施中招募到首次居家访问之间存在长达三周的延迟（在那里收集基线数据）。一些儿童在收集关于这些儿童的其他数据之前就已经在首次居家访问时复发到SAM。因此，对于在招募和首次居家访问之间复发的儿童，将无法评估在首次居家访问时收集的某些时间变化的特征（例如，儿童级健康指标）是否是作为复发的后果而出现的，或者是在复发之前出现的。这是一个局限性，可能会对数据分析产生影响，具体取决于数据用户希望进行的数据分析类型。特别是，如果用户对评估某些因素对复发率的影响感兴趣，则分析不应受到内生性的影响。有几种方法可以处理这种局限性，例如：i）将分析限制在在招募和首次居家访问之间可以合理假设为不变的变量/协变量，或ii）将OTP治愈儿童的时间起点定义为首次居家访问（而不是从卫生设施招募），并将分析限制在首次居家访问时没有复发到SAM的儿童子样本（尽管这会导致样本量显著减少）。
数据清理操作
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由于数据是电子收集的，在整个调查周期中持续进行检查、编辑和处理。
数据检查的第一阶段由调查团队进行，包括：
（i）检查所有ID；
（ii）检查缺失观察值；
（iii）检查不应缺失的项目响应的缺失项响应；
（iv）第一轮检查不可接受/超出范围和不一致值。
在数据收集结束时，进行了额外的数据处理活动，以便将收集到的清洁数据转换为分析准备好的格式。这些活动的目的是产生可靠、一致和完全记录的数据集，可以在整个调查期间进行分析，并在结束时以这种方式存档，以便其他数据用户在未来很好地使用。
数据处理活动包括：
- 重新塑形数据集，以产生每个观察单位的数据文件，
- 通过删除识别受访者的所有变量（如姓名、地址、GPS坐标等）来匿名化数据，
- 使用预先确定的分类方案对非响应进行分类和编码，
- 审查“其他（请说明）”响应，检查是否有任何响应属于现有响应类别并可以重新编码到现有类别，或者是否存在多个类似的“其他”响应需要创建新的响应类别（由数据分析师做出决定），
- 正确命名和标记每个数据集中的变量。
然后将数据集发送到分析团队，在那里它们接受了第二组检查和清理活动。这包括检查超出范围响应和不一致值，这些值没有被CAPI软件中构建的过滤器或调查团队进行的第一轮数据检查过程捕获。
创建了一个全面的数据检查和分析系统，包括逻辑文件夹结构、详细的数据分析指南和模板语法文件（在Stata中），以确保记录数据检查和清理活动，并确保所有分析师适当地使用文件和变量命名约定。
应答率
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在总共招募进研究的645名OTP治愈儿童中，553名在首次居家访问时被发现并被认为是合格的，83名未找到，9名后来被发现不符合资格。
在总共招募进研究的543名社区儿童中（符合资格并被匹配到OTP治愈儿童），17名后来被发现不符合资格（因此被排除）。
因此，本研究的样本量（以及因此发表的数据的观测数）由553名OTP治愈儿童和526名社区对照儿童组成。
就儿童在研究结束时的结果而言：
- 在553名OTP治愈儿童中，378名在研究期间没有经历SAM，因此一直持续到第12次居家访问；134名在访问期间经历了SAM（此时，他们不再被纳入进一步的随访访问）；32名在某个时候退出了研究（3名后来撤回同意，29名不再可追踪）；9名在研究期间死亡（此时，他们不再被纳入进一步的随访访问）。
- 在526名社区对照儿童中，488名在研究期间没有经历SAM，因此一直持续到第12次居家访问；3名在访问期间经历了SAM（此时，他们不再被纳入进一步的随访访问）；30名在某个时候退出了研究（6名后来撤回同意，24名不再可追踪）；5名在研究期间死亡（此时，他们不再被纳入进一步的随访访问）。