Table 3. Predictors of false positive results (using direct fluorescent antibody testing (DFA) as the gold standard) for stool specimens that tested positive for Cryptosporidium infection by Meridian Immunocard Stat! rapid cartridge assay at community laboratories (n = 305).

	Total	Number (%) false positives	Unadjusted OR (95% CI)	Adjusted* OR (95% CI)
Overall	305	139 (45.6%)	NA	NA
Site
New York	116	43 (37.1)	ref	ref
Wisconsin	94	38 (40.4)	1.2 (0.7, 1.9)	0.6 (0.3, 1.2)
Minnesota	95	58 (61.1)	2.7 (1.5, 4.7)	1.6 (1.0, 2.8)
Age Group
≤25	140	31 (22.1)	ref	ref
>25	152	99 (65.1)	6.5 (3.6, 11.7)	6.3 (3.4, 11.7)**
Sex
Male	142	60 (42.3)	ref	ref
Female	150	70 (46.7)	1.2 (0.8, 2.0)	0.8 (0.5, 1.5)
Season
Summer	153	63 (41.2)	ref	ref
Fall, Winter, Spring	148	75 (50.7)	1.5 (0.9, 2.5)	1.7 (0.9, 3.2)
Storage temperature at community laboratory
Room temperature	223	100 (44.8)	ref	ref
Refrigerated (4C)	74	35 (47.3)	1.1 (0.7, 1.9)	0.7 (0.3, 1.5)
Preservative used
10% Formalin	90	35 (38.9)	ref	ref
SAF	100	43 (43.0)	1.2 (0.6, 2.4)	1.4 (0.9, 2.4)
Cary Blair	88	48 (54.6)	2.0 (1.0, 3.7)	3.0 (1.8, 4.9)**
Other***	15	4 (26.7)	0.6 (0.2, 1.3)	0.5 (0.4, 0.7)**
No preservative used	12	9 (75.0)	4.7 (1.0, 21.9)	8.1 (1.9, 35.4)**
Time between collection and testing at community laboratory
Same Day	176	89 (50.6)	ref	ref
Next Day	99	38 (38.4)	0.6 (0.4, 0.9)	0.5 (0.3, 1.0)
2–3 Days	21	9 (42.9)	0.8 (0.3, 2.2)	0.8 (0.2, 2.9)

* Log binomial regression using GEE with an exchangeable correlation matrix was used to account for correlation between isolates from the same lab. The adjusted model included all attributes shown in the table.

** 95% confidence interval for odds ratios did not include the null after adjustment

*** “Other” category included Totalfix, Ecofix, and preservatives described as “Other” with no brand specified.