Serological comparison of purified antigens 60 and 85A (P32) of Mycobacterium bovis BCG, and purified protein derivative, in active pulmonary tuberculosis.

The immunoglobulin G (IgG) response directed against Mycobacterium bovis BCG antigens 60 (A60) and 85A (P32), and purified protein derivative (PPD), was investigated in order to compare the serodiagnostic potentials of these antigens in tuberculosis (TB). The sera of 59 patients with active minimal or moderately advanced pulmonary TB and of 59 healthy control subjects were tested by enzyme-linked immunosorbent assay. The frequencies of positivity were significantly higher (P < 0.001) in patients than in controls and similar with all three antigens. The strongest correlation was found between the responses to A60 and PPD (P < 0.001), the weakest between the responses to A60 and P32 (P < 0.05). Discrepancies were observed in newly diagnosed patients before the institution of specific chemotherapy and in patients with negative direct smears at the time of diagnosis. Untreated patients with negative direct smears presented the lowest sensitivities. P32 was the most effective antigen in diagnosing these cases (50% positivity); A60 was not better than PPD (29% and 21% positivity, respectively). The results presented here emphasize the importance of comparing antigens with the same samples in order to allow their real respective evaluation.