Sero-diagnosis of tuberculosis with A60 antigen enzyme-linked immunosorbent assay: failure in HIV-infected individuals in Ghana

ABSTRACT

In order to assess the diagnostic usefulness of the A60 (ANDA Biological; Strassbourg; France) sero-diagnostic enzyme-linked immunosorbent assay (ELISA) kit for tuberculosis in Africa; sera of 53 pulmonary smear-positive tuberculosis (TB) patients; 30 apparently healthy control subjects and 6 AIDS suspects were sampled in Agogo Hospital in the forest area of Ghana. These sera were analyzed for antibodies to HIV-1 and HIV-2; and IgG-antibodies to the A60 BCG-antigen; while the non-HIV individuals were tested for total IgG levels. One healthy control subject; all of 6 AIDS suspects and 7 of the TB patients has HIV infections. In the non-HIV TB group; the sensitivity and specifity of the A60 ELISA was 78 per cent and 86 per cent; respectively; which was much poorer than expected from published reports about the A60 test. The A60 test failed; completely however; to discriminate between TB and non-TB in the HIV-positive group. In the non-HIV groups; total IgG levels were significantly higher in TB patients than in controls. It seems that the usefulness of the A60 ELISA test to diagnose tuberculosis is very limited in this high-incidence area; and that it seems to be of no value in patients infected with HIV