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Participant Blinding And Gastrointestinal Illness In A Randomized, Controlled Trial Of An In-Home Drinking Water Intervention, John M. Colford, Judy R. Rees, Timothy J. Wade, Asheena Khalakdina, Joan F. Hilton, Isaac J. Ergas, Susan Burns, Anne Benker, Catherine Ma, Cliff Bowen, Daniel C. Mills, Duc J. Vugia, Dennis D. Juranek, Deborah A. Levy

Journal Articles: Epidemiology

We conducted a randomized, triple-blinded home drinking water intervention trial to determine if a large study could be undertaken while successfully blinding participants. Households were randomized 50:50 to use externally identical active or sham treatment devices. We measured the effectiveness of blinding of participants by using a published blinding index in which values >0.5 indicate successful blinding. The principal health outcome measured was "highly credible gastrointestinal illness" (HCGI). Participants (n=236) from 77 households were successfully blinded to their treatment assignment. At the end of the study, the blinding index was 0.64 (95% confidence interval 0.51-0.78). There were 103 episodes of …