Screening test: Negative (reported as negative, positive or equivocal)
Negative: Indicates antibodies to histoplasma were not detected.
The absence of antibodies is presumptive evidence that the patient
was not infected with histoplasma. However, the specimen may have been drawn before antibodies were detectable, or the patient may be immunosuppressed. If infection is suspected, another specimen should be drawn 7 to 14 days later and tested.
Equivocal: Specimens with equivocal enzyme immunoassay (EIA) results will be tested by complement fixation and immunodiffusion.
Positive: The presence of antibodies is presumptive evidence that the patient was previously or is currently infected with (or exposed to) histoplasma. These specimens will be tested by complement fixation and immunodiffusion for confirmation.
Complement Fixation/Immunodiffusion test:
Mycelial by complement fixation: negative (positives reported as titer)
Yeast by complement fixation: negative (positives reported as titer)
Antibody by immunodiffusion: negative (positives reported as band present)
Complement fixation (CF) titers ≥1:32 indicate active disease. A rising CF titer is associated with progressive infection.
Positive immunodiffusion test results supplement CF test result.
Patients infected with H. capsulatum demonstrate a serum antibody with a rising titer within 6 weeks of infection. A rising titer is associated with progressive infection. Specific antibody persists for a few weeks to a year, regardless of clinical improvement.