96T

serum

Human

The Coccidioides Antibody Enzyme Immunoassay (EIA) is used for the qualitative detection of serum antibodies directed against TP and CF antigens from Coccidioides species as an aid in the diagnosis of coccidioidomycosis.

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.

In a separate study, the relative sensitivity and specificity of the Coccidioides Antibody EIA were evaluated versus Coccidioides immunodiffusion (ID). A total of 85 Coccidioides ID-positive samples (IDCF identity band) was tested on the Coccidioides Antibody EIA following the package insert. Of the specimens that were ID-positive, 97.6% were found to be positive using the Coccidioides Antibody EIA. The remaining 2.4% of the specimens fell into the indeterminate range. None of the ID- positive specimens yielded a negative result in the EIA.

*Negative result indicates the specimen was negative for both CF and TP.
**Indeterminate result indicates the specimen was negative for either CF or TP and indeterminate for the other, or indeterminate on both CF and TP.
***Positive result indicates the specimen was positive for CF, TP, or both.

Coccidioides species are dimorphic fungi that exist as either mycelia (saprobic growth) or spherules (parasitic growth) which cause respiratory diseases and occasionally diseases affecting other systems (1). Though endemic in the southwestern United States and Mexico, increased travel to the endemic areas has also increased the incidence in nonendemic areas (1,2). Coccidioidomycosis should be considered whenever patients display symptoms of pulmonary or meningeal infection and have lived or traveled to the endemic areas (3).
Coccidioidomycosis presents a diagnostic challenge to the physician and laboratorian. The manifestations of most early coccidioidal infections substantially overlap with those of other respiratory infections (4). In addition, culturally and histologically, the organisms can be difficult to demonstrate, even after repeated attempts (1, 2). Therefore, specific laboratory testing is usually required to establish a diagnosis of coccidioidomycosis.
Serologic tests have served for several decades as aids in the diagnosis and management of coccidioidomycosis (1). Complement fixation (CF), immunodiffusion (ID), and latex agglutination (LA) have been the most commonly used serologic methods. The CF assay is sensitive; however, its performance is complex and labor-intensive. Additionally, the CF assay exhibits low specificity due to cross-reactive antibodies which recognize carbohydrate moieties common to several fungi. The ID assay is more specific but less sensitive than the CF assay; additionally, the ID assay takes 48 hours to perform and requires highly skilled personnel to properly interpret results. The LA assay is sensitive and rapid but lacks specificity. However, the Coccidioides Antibody EIA is a sensitive, specific, and rapid test for the qualitative detection of TP and CF antibodies against antigens from Coccidioides.