MVISTA® Histoplasma Feline IgG Antibody EIA
A 5-year-old DSH from south Texas had been treated two years prior for chronic diarrhea due to histoplasmosis. At that time, Histoplasma capsulatum yeasts were identified on histopathology. The DVM was concerned about a relapse of the disease since similar clinical signs had been recently observed, although he also considered other differential diagnoses as the cause of current diarrhea. Urine Histoplasma antigen test result was very low positive (<0.4 ng/mL). This result has a low positive predictive value, as it is just above the assay cutoff; therefore, such a result may be viewed as “equivocal.” Serum from this cat was submitted for the Histoplasma Feline IgG antibody EIA, and anti-Histoplasma antibody was moderately positive (38 EIA units). The combination of low positive antigen and moderately positive antibody was evidence of ongoing histoplasmosis.
Preliminary unpublished studies using MVista® Histoplasma Feline IgG Antibody EIA:
TEST CODE: 328
CLINICAL SIGNIFICANCE: IgG antibodies to Histoplasma antigen appear to be associated with active infection, especially in cats with moderate to high positive (20 EU or greater) results. Antibodies may also be detected in a small percentage of healthy cats from the endemic area as a result of sub-clinical infection within the last 2 years. IgG may be detected in histoplasmosis cases with falsely-negative antigen results (especially with localized disease or chronic infection) and combined antibody and antigen testing increases the overall sensitivity. Intermediate results (8-9.9 EU) typically reflect either rising or falling IgG, and retesting the patient in several weeks may be beneficial.
MINIMUM SPECIMEN REQUIREMENTS:
SPECIMEN REJECTION: CSF and plasma are tested as rare specimens. For specimen submissions that do not meet these criteria, please call Customer Service.
TRANSPORT TEMPERATURE: Refrigerated/Frozen
SHIPPING: Place the specimen and test requisition form in a waterproof, sealable specimen bag. Place the specimen bag and cold pack in a styrofoam container in a box. Ship overnight or second day.
Testing is performed on Tuesdays & Thursdays
Serum or CSF: Same or Next Day
REFERENCE RANGE: Negative
Semi-Quantitative Indirect Enzyme Immunoassay
~1/3 of patients with blastomycosis or coccidioidomycosis will exhibit cross reactivity. The reference range and other method performance specifications have not been established for this test in CSF. The test results should be integrated into the clinical context for interpretation.