1. Participant blinding and gastrointestinal illness in a randomized, controlled trial of an in-home drinking water intervention.
- Author
-
Colford JM Jr, Rees JR, Wade TJ, Khalakdina A, Hilton JF, Ergas IJ, Burns S, Benker A, Ma C, Bowen C, Mills DC, Vugia DJ, Juranek DD, and Levy DA
- Subjects
- Adolescent, Adult, Aged, California, Child, Double-Blind Method, Drinking, Feasibility Studies, Female, Gastrointestinal Diseases diagnosis, Humans, Male, Middle Aged, Pilot Projects, Quality Control, Surveys and Questionnaires, Water Supply, Gastrointestinal Diseases etiology, Water Purification standards
- Abstract
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 HCGI during 10,790 person-days at risk in the sham group and 82 episodes during 11,380 person-days at risk in the active treatment group. The incidence rate ratio of disease (adjusted for the clustered sampling) was 1.32 (95% CI 0.75, 2.33) and the attributable risk was 0.24 (95% CI -0.33, 0.57). These data confirm that participants can be successfully blinded to treatment group assignment during a randomized trial of an in-home drinking water intervention.
- Published
- 2002