Evaluation of a monoclonal antibody (TB72) based serological test for tuberculosis.

A serological test for tuberculosis (TB), based on competitive inhibition by human sera of antigen binding by a murine monoclonal antibody (TB72) has been performed using solid phase radioimmunoassay. The test was evaluated on sera from patients with pulmonary or extra-pulmonary active TB as well as from control hospitalized patients--half of whom had various chest complaints. Positive values were found in 74% of all or 55% of untreated active pulmonary TB. Patients with extrapulmonary TB segregated, whereby antibody titres were increased in cases of pleural, peritoneal, pericardial or bone infection but only marginal or negative values were found in the majority of patients with lymphatic and genitourinary infection. None of the subjects with suspected but excluded tuberculosis or sarcoidosis had demonstrable TB72 antibodies. Generally there was a positive correlation between the levels of TB72 like and 'total' Mycobacterium tuberculosis sonicate binding antibodies. In particular, the titre of sonicate binding antibodies did not exceed background levels in patients with active pulmonary tuberculosis who were negative in the TB72 competition test. None of these false negative patients received drug therapy whereas most patients with the highest antibody levels were under chemotherapy for 1-8 months prior to serum testing. The serodiagnostic value of the TB72 based competition test has been discussed.