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Volume 8, Number 1—January 2002

Research

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

John M. Colford*†Comments to Author , 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¶, and Deborah A. Levy¶
Author affiliations: *University of California Berkeley, Berkeley, California, USA; †California Emerging Infections Program, Berkeley, California, USA; ‡University of California San Francisco, School of Medicine, San Francisco, California, USA §California Department of Health Services, Berkeley, California, USA; ¶Centers for Disease Control and Prevention, Atlanta, Georgia, USA;

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Table 3

Episodesa of highly credible gastrointestinal illness (HCGI) and days of illness, Pilot Water Evaluation Trial

Sham device group Active device group Total
Total episodes of HCGI, defined byb 103 82 185
Vomiting 18 30 48
Watery diarrhea 73 42 115
Soft diarrhea with abdominal cramps 7 6 13
Nausea with abdominal cramps 16 17 33
Total days of HCGI, defined byb 261 190 451
Vomiting 35 78 113
Watery diarrhea 207 99 306
Soft diarrhea with abdominal cramps 8 8 16
Nausea with abdominal cramps 31 30 61
Total days at risk for HCGI episodes 10,790 11,380 22,170
Total days of observation 11,642 12,036 23,678

aA new episode was defined as the presence of any of four definitions of HCGI, preceded by 6 HCGI-free days. The difference in total episodes of HCGI was the principal a priori health outcome measure for the study.

bBecause individual participants could report multiple definitions of HCGI on the same day, the total episodes of HCGI (and total days of HCGI) are less than the sums of the individual definitions.

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