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# Table 2 Unadjusted, matched odds ratios for the occurrence of cryptosporidiosis among patients with AIDS according to exposure to drinking water sources

Cases (n = 49) Controls (n = 99)
Variable N (%) N (%) Odds Ratio 95% CI
Tap water at home
Never 2 (4) 31 (31) 1.00 Reference
Sometimes 20 (41) 30 (30) 9.54 2.06, 44.1
Always 27 (55) 38 (38) 9.78 2.14, 44.7
Tap water outside home
Never 29 (59) 81 (82) 1.00 Reference
Sometimes 4 (8) 8 (8) 2.00 0.53, 7.50
Always 16 (33) 10 (10) 4.20 1.76, 10.0
Tap water compositea
Lowest exposure 2 (4) 29 (29) 1.00 Reference
Intermediate exposure 35 (71) 64 (65) 7.08 1.59, 31.4
Highest exposure 12 (24) 6 (6) 24.3 4.21, 139
Bottled water at home
Never 25 (51) 38 (38) 1.00 Reference
Sometimes 24 (49) 40 (40) 0.81 0.37, 1.76
Always 0 (0) 21 (21) 0.09c 0.03, 0.37
Bottled water outside home
Never 17 (35) 36 (36) 1.00 Reference
Sometimes 10 (20) 20 (20) 0.97 0.28, 3.40
Always 22 (45) 43 (43) 0.75 0.28, 2.06
Bottled water compositeb
Lowest exposure 11 (22) 17 (17) 1.00 Reference
Intermediate exposure 38 (78) 70 (71) 0.66 0.26, 1.68
Highest exposure 0 (0) 12 (12) 0.17c 0.06, 0.83
Filtered municipal water
Filtered 27 (55) 51 (52) 1.00 Reference
Mixed 14 (29) 37 (37) 0.75 0.35, 1.58
Unfiltered 8 (16) 11 (11) 1.36 0.44, 4.16
1. aLowest = answered never consumed tap water both inside and outside the home; Highest = answered always consumed tap water both inside and outside the home; Intermediate = all other responses bLowest = answered never consumed bottled water both inside and outside the home; Highest = answered always consumed bottled water both inside and outside the home; Intermediate = all other responses cUnmatched, median-unbiased odds ratio estimate and exact 95% confidence intervals calculated directly from the mid-p function based on the hypergeometric model (see methods)