SERODIAGNOSTIC TESTS IN TUBERCULOSIS

Summary: The problem of development of serological tests in detection of tuberculosis is an old one. Techniques involving detection of antibodies have inherent disadvantages. It is often difficult to distinguish normal people with BCG Vaccination from tubercular patients. The more sensi-tive the assay, the greater is the problem of differentiation. Since antibodies persist for a long time after bacillary clearance, antibody levels cannot differentiate between active disease and healed lesion. Monoclonal antibodies produced to a specific single epitope of the bacillus is the newest entrant in the field. Extensive studies need to be done to establish its efficacy in clinical practice. The detection of antigen is a better proof of infection than antibody assay. Tests have been develop-ed to detect antigen as well as antibody which are sensitive and specific at least for M. Tuberculosis and M. Bovis. Antigen could be detected in patients with positive sputum but not in controls; in bronchial aspirates of tubercular patients and in pleural and ascitic fluids of tubercular origin. Antigen detection yield was poor in CSF and in patients with high antibody levels in pleuia! and ascitic fluids. In such situations specific antitubercular antibody has proved a better diagnostic inde.i to detect disease. Detection of specific tubercular antigen and antibody in circulating immune comp-lexes correlated with presence of infection. Antigen detection is not only useful to identify presenc