Enzyme-linked immunosorbent assay using Mycobacterium tuberculosis antigen 5 and PPD for the serodiagnosis of tuberculosis.

Enzyme-linked immunosorbent assays (ELISA) of immunoglobulin G antibody to Mycobacterium tuberculosis antigen 5 and tuberculin purified protein derivative (PPD) were assessed for the serodiagnosis of tuberculosis in 41 patients with active tuberculosis, 19 patients with inactive tuberculosis, and 59 healthy control subjects. Patients with active tuberculosis were studied serially at monthly intervals following the initiation of therapy. When contrasted with our earlier studies of sera from patients in Bolivia and Argentina, serum titers in Cleveland patients with active tuberculosis were somewhat lower. Geometric mean titer in patients with active tuberculosis was 1:68 with antigen 5 and 1:46 with PPD. Titer was correlated with patient age, male sex, extent of tuberculosis, and history of prior tuberculosis. However, these associations were not statistically significant. During monthly follow-up for 16 months after the initiation of therapy, ELISA titers remained essentially stable. Thus, no convincing evidence was acquired to support the hypothesis that higher titers in sera from South American patients related to more chronic or more extensive disease. Receiver operating characteristics of ELISA with antigen 5 were better than those obtained using PPD and were similar to those reported by others for sputum smear. In a situation where tuberculosis screening is warranted, ELISA with antigen 5 might have a place if it recognizes a different population than does sputum smear.