Serology of tuberculosis. 11. measurement of antibodies to Myobacterium tuberculosis by a passive haemagglutination test in human tuberculosis

A simple and sensitive passive haemagglutination (PHA) test has been evaluated in the serology of human tuberculosis. Double aldehyde stabilized red cells were sensitized with cell extracts and PPD antigens from M. tuberculosis (H37Rv) and used as reagents in the test. The study was conducted on sera from 71 bacteriologically confirmed cases of tuberculosis and their controls, inclusive of 59 healthy blood donors and 28 non-tuberculous chest disease patients. In addition, 318 random samples of sera and 107 finger prick blood samples collected on filter papers from apparently healthy people were examined. For comparative evaluation, tuberculous patients' sera were examined by enzyme linked immunosorbent assay (ELISA) and crossed immunoelectrophoresis (CIE). The distribution of IgG and IgM type anti-mycobacterial antibodies (AMA) in tuberculous patients' sera was evaluated by a modified PHA test. The results of the study indicated that the PHA test was a sensitive method for the quantitation of antibodies, which could be demonstrated in all groups of sera studied. The PHA test and ELISA with the antigens used were not found to be specific enough for the serodiagnosis of tuberculosis; the results indicated the need to investigate several immunological approaches for this purpose. Both tests did differentiate between the mean AMA levels of tuberculous patients and their controls and both showed treated and relapsed cases of tuberculosis to contain higher serum levels of antibodies than did new cases. Both tests were found to be more sensitive than CIE with the intermediate gel technique. The PHA test was found to be sensitive enough for the measurement of antibodies in finger-prick blood samples, indicating its potential for field studies.