Serological diagnosis of tuberculosis

Abstract

The past decade has seen dramatic developments in serological tests for tuberculosis. The long history of serological tests for tuberculosis is a testimony to the need for a sensitive diagnostic test, especially when the sputum smear is unhelpful. New reagents, both purified antigens and monoclonal antibodies, provide the means to obtain a sensitivity and specificity to rival the tuberculin skin test and equal other commonly used diagnostic blood tests. Evaluation with sera from patients with smear-positive pulmonary tuberculosis has identified one antigen (antigen 5, the 38 kDa antigen) as a potential screening reagent for infectious tuberculosis and another (16 kDa antigen) for monitoring compliance. A monoclonal antibody competition assay anti-38 kDa antibody is the most sensitive serological test for smear-negative tuberculosis so far. Tests for tuberculous meningitis need clinical evaluation. Serological tests for human immunodeficiency virus (HIV)-related tuberculosis are disappointing. In general, antibody levels in primary tuberculosis are low and appear directed towards cytoplasmic antigens, whilst in post-primary disease antibody levels are higher and appear to bind to secreted antigens. No single reagent gives a 100% sensitivity; future research should identify the best combination of antigens for the serodiagnosis of tuberculosis.