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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 1

Baseline characteristics of 236 participants in Pilot Water Evaluation Trial

Characteristic Sham
(n = 118) Active
(n = 118)
Age (Years) n (%) n (%)
<11 28 (24) 29 (25)
12-19 10 (8) 13 (11)
20-29 9 (8) 4 (3)
30-39 22 (19) 18 (15)
40-49 21 (18) 24 (20)
50-59 16 (14) 14 (12)
>60 12 (10) 16 (14)
Sex (%) n (%) n (%)
Female 57 (48) 56 (48)
Male 61 (52) 62 (52)
Prior medical conditions n (%) n (%)
Crohn’s disease 1 (1) 0 (0)
Diverticulitis 1 (1) 3 (3)
Frequent heartburn 5 (4) 8 (7)
Irritable bowel syndrome 7 (6) 2 (2)
Milk intolerance 4 (3) 5 (4)
Stomach ulcer 5 (4) 4 (3)
Ulcerative colitis 0 (0) 1 (1)
Migraine headaches 14 (12) 13 (11)
Self-assessment of current health n (%) n (%)
Excellent 42 (36) 41 (35)
Very good 54 (46) 53 (45)
Good 20 (17) 20 (17)
Fair 2 (2) 4 (3)
Poor 0 (0) 0 (0)
Current medical conditions (prior 7 days) n (%) n (%)
Abdominal cramps 19 (16) 15 (13)
Diarrhea 14 (12) 13 (11)
Nausea 16 (14) 11 (9)
Vomiting 2 (2) 3 (3)
Fever 6 (5) 5 (4)
Pregnant 1 (1) 1 (1)

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