Defining episodes of diarrhoea: results from a three-country study in sub-Saharan Africa

The study was conducted to assess the effect of definition of episode on diarrhoeal morbidity and to develop a means of adjusting estimates of morbidity for the definition of episode used. This paper reports on a cohort study of 374 children, aged 9-32 months, in three African countries, which recorded frequency and consistency of stool over a seven-month period. Different definitions of episode were applied to these data to assess their effect on annualized diarrhoeal morbidity. Adjustment factors were then derived that corrected morbidity for non-standard definitions of episode. Applying non-standard definitions of episode gave estimates of an annualized number of episodes between 38% and 137% of the internationally-accepted definition. Researchers should be encouraged to use the standard definition of episode of diarrhoea and to use appropriate field protocols. Where this is not possible, correction factors should be applied, particularly where estimates of diarrhoeal morbidity are pooled in systematic reviews.