False-Positive Complement-Fixation Serology in Histoplasmosis

A review of the records of 79 consecutive patients who had a positive immunodiffusion or complement-fixation test for histoplasmosis showed 28 (35%) with false-positive serologic results in relation to their clinical significance. Twelve patients (15%) had complement-fixation titers of 1:32 or greater, without cultural or histological evidence of active infection. No common clinical or laboratory finding could be correlated with the presence of false-positive tests. The latter finding correlates well with the incidence of false-positive complement-fixation titers (12%) in the normal random patient population. (JAMA239:2453-2456, 1978)