Participant Blinding and Gastrointestinal Illness in a Randomized, Controlled Trial of an In-Home Drinking Water Intervention

Authors

John M. Colford, University of California - Berkeley
Judy R. Rees, University of California - Berkeley
Timothy J. Wade, University of California - Berkeley
Asheena Khalakdina, University of California - Berkeley
Joan F. Hilton, University of California, San Francisco
Isaac J. Ergas, University of California - Berkeley
Susan Burns, University of California - Berkeley
Anne Benker, University of California - Berkeley
Catherine Ma, California Department of Health Services
Cliff Bowen, California Department of Health Services
Daniel C. Mills, California Department of Health Services
Duc J. Vugia, California Department of Health Services
Dennis D. Juranek, Centers for Disease Control and Prevention
Deborah A. Levy, University of Nebraska Medical CenterFollow

Document Type

Article

Journal Title

Emerging Infectious Diseases

Publication Date

2002

Volume

8

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.

DOI Link

10.3201/eid0801.001481

ISSN

1080-6040

Creative Commons License

This work is licensed under a Creative Commons Public Domain Dedication 1.0 License.

Rights

U.S. Government Work

Recommended Citation

Colford, John M.; Rees, Judy R.; Wade, Timothy J.; Khalakdina, Asheena; Hilton, Joan F.; Ergas, Isaac J.; Burns, Susan; Benker, Anne; Ma, Catherine; Bowen, Cliff; Mills, Daniel C.; Vugia, Duc J.; Juranek, Dennis D.; and Levy, Deborah A., "Participant Blinding and Gastrointestinal Illness in a Randomized, Controlled Trial of an In-Home Drinking Water Intervention" (2002). Journal Articles: Epidemiology. 98.
https://digitalcommons.unmc.edu/coph_epidem_articles/98