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Table 1 Descriptions of the assumptions underlying AACF and study procedures to reduce potential violations

From: Active and adaptive case finding to estimate therapeutic program coverage for severe acute malnutrition: a capture-recapture study

Assumption

Description

Study procedure

Closed population

The population sampled using both methods is the same. In this case the same households are considered during each day of case finding, there are no absent cases on either day and only residents of the village are considered.

- The same guide was used to ensure the same village boundaries were used on both days.

- The second day of case finding was performed immediately after the first day limiting the possibility of movements of people in between samples.

- On the first day of sampling all cases found were encouraged to remain at home the following day and the village leader was also requested to communicate the same message to limit the amount of absent cases on the second day.

- Known market and treatment days were avoided for both first and second days of case finding, and on the first day village leaders were asked whether there was likely to be significant movements of people (to a market for example).

- All cases were proven (by asking mother and double checking with village leader, or other informant) to be from the selected village.

Ability to perfectly match cases captured in both methods

Cases found in both samples can be reliably identified and there is certainty when a case is only found in one sample.

- Four matching variables (first and second name, age and sex of child) were collected during both samples.

Perfect classification (Perfect diagnosis of SAM and coverage status in both methods)

Cases are correctly identified and there is no over or under diagnosis of cases.

- A rigorous, clear and context specific case definition was developed prior to the study.

- Surveyors were trained in case identification, including screening for SAM by mid-upper arm circumference (MUAC) measurements and edema testing, and screening for recovering cases by asking carers to present sachets of ready-to-use therapeutic food (RUTF) or clearly explain treatment schedule.

Equal probabilityof capture within a method

All cases should have the same chance of being found including very sick or hidden children.

- If any suspected cases were away at the time of the household visit teams returned at the end of the day in case they had returned.

- The survey team conducted a quick census at each household visited to ensure there were no children sleeping or being hidden.

- If children were not present in the household but were nearby they were found by the survey team.

Independence of capture between methods

When a child is found in the first sample, this does not increase (positive dependence) or decrease (negative dependence) the likelihood of being found in the second sample.

- Assured given systematic sampling conducted during census method.