RELATIVE SENSITIVITY AND SPECIFICITY TO COMPLEMENT FIXATION (N=716)
The relative sensitivity and specificity of the Coccidioides Antibody EIA were evaluated versus Coccidioides complement fixation (CF). A total of 716 specimens was tested using the Coccidioides Antibody EIA. The sample set consisted of 554 samples representing a normal population, 120 Coccidioides CF-positive samples with CF titers ranging from 1:2 through 1:256, and 42 samples from patients identified as positive for other fungal infections by immunodiffusion (ID) testing.

Indeterminate results (Cocci-positive patients, n=5; Cocci-negative patients, n=7) were excluded from the sensitivity, specificity, PPV, and NPV calculations. Calculations were based on a comparison with a normal population; therefore, specimens exhibiting cross-reactivity for other fungal infections (n=42) were excluded from the table above. *Patients were classified as positive for Coccidioides antibody when the complement fixation (CF) test yielded a titer of 1:2 or greater.

*Negative result indicates the specimen was negative for both CF and TP.
**Indeterminate result indicates the specimen was negative for either the CF or TP test and indeterminate for the other, or indeterminate for both CF & TP.
***Positive result indicates the specimen was positive for CF, TP, or both.
Due to the equivocal nature of low titer CF-positive results, the data was analyzed to determine sensitivity and specificity for data subsets consisting of Coccidioides CF-positive specimens categorized according to titer. When the CF titer of the Coccidioides-positive specimen was greater than or equal to 1:4, which was the case in 88 of the 120 Coccidioides specimens, 95.4% of the specimens were identified as positive and the remaining 4.6% fell in the indeterminate range. None of the specimens with a CF titer of 1:4 or greater was identified as negative.
When the CF titer of the Coccidioides-positive specimen was greater than or equal to 1:8, which was the case in 69 of the 120 specimens, 100% of the samples were identified as positive. None of the specimens with a CF titer of 1:8 or greater was identified as negative or indeterminate.

*A negative result indicates the specimen was negative both for CF and TP.
** An Indeterminate result indicates that the specimen was negative for either the CF or TP test and indeterminate for either CF or TP or both.
***A positive result indicates that the specimen was positive for CF, TP, or both.
The high sensitivity and specificity of the Coccidioides Antibody EIA are achieved by utilizing separate antigen preparations for the detection of anti-CF and anti-TP antibodies. As a result, there is some variation in the sensitivities and specificities of the different antigen preparations. The data from the 716 specimens that were tested using the Coccidioides Antibody EIA was analyzed for sensitivity and specificity of the individual antigen preparations. A summary of this analysis is included in the table below.
