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, Ma Catherine, Cliff Bowen, Daniel C. Mills, Duc J. Vugia, Dennis D. Juranek, Deborah A. Levy

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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% Cl 0.75, 2.33) and the attributable risk was 0.24 (95% Cl -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.

Original languageEnglish (US)
Pages (from-to)29-36
Number of pages8
JournalEmerging infectious diseases
Volume8
Issue number1
StatePublished - Feb 5 2002

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ASJC Scopus subject areas

  • Epidemiology
  • Microbiology (medical)
  • Infectious Diseases

Cite this

Colford, J. M., Rees, J. R., Wade, T. J., Khalakdina, A., Hilton, J. F., Ergas, I. J., Burns, S., Benker, A., Catherine, M., Bowen, C., Mills, D. C., Vugia, D. J., Juranek, D. D., & Levy, D. A. (2002). Participant blinding and gastrointestinal illness in a randomized, controlled trial of an in-home drinking water intervention. Emerging infectious diseases, 8(1), 29-36.