Comparison of self-reported and observed water contact in an S-mansoni endemic village in Brazil

Estimates of exposure are critical for immuno-epidemiologic and interventio n studies in human schistosomiasis. Direct observation of human water conta ct patterns is both costly and rime consuming. To address these issues, we determined whether individuals residing in a Schistosoma mansoni endemic vi llage in Brazil could accurately self-report their water contact patterns. We compared the results of a water contact questionnaire to the present gol d standard, direct observation of water contact in 86 volunteers, aged 8'9. We administered a survey to estimate volunteers' frequency and type of wat er contact and directly measured each volunteers water contact patterns dur ing 5 weeks of detailed water contact observations. We found a poor correla tion between self reported frequency of contact and directly observed expos ure (rho = 0.119. P = NS). The questionnaire data was supplemented by infor mation about average body surface area of exposure and duration of contact for specific activities derived from observations of this cohort. This 'sup plemented questionnaire' data was significantly correlated with their expos ure index (rho = 0.227, P = 0.05). It provides a starring point from which questionnaires may develop to provide a more cost-effective and less labor intensive method of assessing water contact exposure at the level of the in dividual. (C) 2001 Elsevier Science B.V. All rights reserved.