RESUMO
Several methodological issues may have an impact on the incidence rates of childhood acute diarrhea reported by community-based studies. This study was performed to assess the impact of parental recall ability and definition of diarrhea on the estimate of incidence of acute diarrhea. Eighty-four children younger than 40 months were randomly selected and visited every other day for four weeks and the occurrence of diarrhea was registered. On the last day of the study, another visit was performed and the informants were inquired about the occurrence of diarrhea during the previous four weeks. Data gathered during the four weeks were compared to those obtained on the last visit. Additionally, the informants' definition of diarrhea was investigated and compared to the one adopted by this study. During the observation period, 33 children suffered diarrhea, but only 10 (30.3 percent) informants reported the occurrence of diarrhea. Although 42.4 percent of those informants reported that their children had been ill over that period, they did not report diarrhea. Further, 60.6 percent children who had diarrhea suffered at least one episode in the two weeks prior to the visitation. The same definition of diarrhea used in this study was adopted by 52.1 percent of the informants inquired. Parental recall is an unreliable method to estimate the incidence of diarrhea and studies with a short interval between the visits should be necessary to correctly evaluate this important health problem. Moreover, assessing the informants' own definition of diarrhea is a significant contribution to the interpretation of the results.