title: Significance of false-positive serologic tests for histoplasmosis and blastomycosis in an endemic area.
abstract: False-positive serologic tests for histoplasmosis (H) and blastomycosis (B) are common in populations from endemic areas. In order to determine the significance of false-positive test results, we reviewed the final diagnoses of all patients whose sera were submitted to our laboratory for radioimmunoassay (RIA) and immunodiffusion (ID) during a 3-yr period. Of the 263 patients whose sera were examined, 29 (11%) had H or B; 41 (17.5%) of the remaining 234 patients had false-positive test results. Of these 41 patients, 31 were positive for H alone, and 10 had antibodies to both H and B. All three patients with false-positive ID tests for histoplasmosis also had positive titers (greater than or equal to 1:16) on RIA. No patient had a false-positive ID result for blastomycosis. The percentage of patients in each of five major diagnostic categories with and without false-positive serologic tests was similar (p greater than 0.05). The majority of patients had pulmonary infections, almost half of which were granulomatous infections other than H or B; this reflects the clinical indications for requesting fungal serologic tests. A positive fungal serology is not useful in suggesting the presence of a pulmonary disease other than H or B in patients from an endemic area suspected of having a pulmonary mycosis.
authors.affiliation: Department of Medicine, Louisiana State University School of Medicine, Shreveport 71130.
authors.forename: M M
authors.initials: MM
authors.lastname: Jordan
authors.forename: J
authors.initials: J
authors.lastname: Chawla
authors.forename: M W
authors.initials: MW
authors.lastname: Owens
authors.forename: R B
authors.initials: RB
authors.lastname: George
mesh_terms: D001759:Blastomycosis / Q000175:diagnosis / Q000453:epidemiology*; D005189:False Positive Reactions; D005260:Female; D006660:Histoplasmosis / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D005779:Immunodiffusion; D008145:Louisiana / Q000453:epidemiology; D008172:Lung Diseases, Fungal / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011863:Radioimmunoassay