Anti-A60 immunoglobulin G in the serodiagnosis of tuberculosis in HIV-seropositive and seronegative patients

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Abstract
A60 is a high molecular weight mycobacterial antigen complex. The detection of immunoglobulin (Ig) G antibodies to A60 has been advocated as a reasonably sensitive and specific test for active tuberculosis (TB). We aimed to compare the sensitivity of this test among HIV-seropositive and HIV-seronegative patients with pulmonary TB. The presence and concentration of anti-A60 IgG antibodies was assessed by enzyme-linked immunosorbent assay in 208 HIV-seropositive and 91 HIV-seronegative Zaïrian patients with smear-positive pulmonary TB. The relationship between anti-A60 IgG levels and HIV serostatus, CD4+ lymphocyte counts, presence of clinical AIDS, and tuberculin skin test results was verified. Only 36.5% of the HIV-seropositive, compared with 69.2% of the HIV-seronegative patients had a positive anti-A60 IgG test (P < 0.00001). Among HIV-seropositive patients, anti-A60 IgG levels did not differ according to CD4+ lymphocyte counts, presence of clinical AIDS, or tuberculin skin test results. Among patients with pulmonary TB, the sensitivity of testing for anti-A60 IgG was much lower among HIV-seropositive than among HIV-seronegative patients, even from the early stages of HIV-related immunodeficiency. This limits the utility of anti-A60 IgG-antibody testing in the diagnosis of TB among HIV-infected patients.

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