Judging the quality of survey estimates of mortality
(go to Outline)In acute humanitarian emergencies, prospective mortality reporting has substantial limitations, and measuring retrospective mortality in surveys is one of the most difficult tasks faced by epidemiologists. Nonetheless, scientific epidemiologic principles must be applied in evaluating the validity of any mortality estimate. No mortality estimate can be rejected simply because it seems too high or too low.
When evaluating the mortality estimate from prospective surveillance, ask yourself a few questions:
- How complete is death reporting? Are deaths only reported from health facilities or are other, community-based sources of deaths used?
- How valid is the population denominator used to calculate the mortality rate? If it is likely to be an under- or overestimate, the mortality rate may be over- or underestimated.
- If the mortality rate has changed, is it due solely to a change in the denominator?
When evaluating the results of a survey measuring mortality, ask yourself these questions:
- Is the sample representative of the entire population? For example, some surveys for which the major objective is assessing the nutritional status of young children may include only households in which an eligible child lives. This sample of households is NOT representative of all households and may give you a biased estimate of the crude mortality rate.
- How were the mortality data collected? If the survey did not follow recommended procedures, the estimates of mortality rates may be biased. (For more information on these procedures, see section on Mortality - Surveys (retrospective data collection).)
- Did the survey managers appropriately interpret the estimated mortality rate? Have they collected additional data to clarify why mortality is elevated. It is not enough to demonstrate elevated mortality without making recommendations for action.
For a more detailed list of criteria useful in judging the quality of mortality estimates from surveillance and surveys, click here.
For a much more detailed discussion of many issues in measuring mortality in humanitarian emergencies, see Checchi F and Roberts L. Interpreting and using mortality data in humanitarian emergencies: a primer for non-epidemiologists. Humanitarian Practice Network No. 25. Overseas Development Institute, 2005. (Click here to open this document.)