Objective: To evaluate antibody responses to panels of Mycobacterium tuberculosis antigens for serological diagnosis of active tuberculosis (TB).
Design: We cloned, expressed and purified 10 M. tuberculosis recombinant proteins 38KD, MPT32 (M. tuberculosis protein 32), MPT64, EspC (ESX-1 secretion-associated protein), Mtb81, Rv3881, Rv3425, Rv0222, Rv3872 and CFP21 (culture filtrate protein 21), and obtained lipoarabinomannan (LAM) polysaccharide antigen from BEI Resources. The plasma immunoglobulin (Ig)G titre responses to the 11 antigens based on 45 patients with pulmonary TB (PTB) and 30 healthy controls (HCs) were first evaluated using enzyme-linked immunosorbent assays. Antigens with high sensitivities were then selected for further investigation in 200 PTB patients (121 smear- or culture-positive patients, 79 smear- or culture-negative patients) and 152 HCs.
Results: LAM, 38KD, MPT32, MPT64, EspC and Mtb81 were chosen. The LAM, 38KD, MPT32 and EspC IgG titres were significantly higher in Bacterium-negative TB patients than in HCs, except for MPT64 and Mtb81. The sensitivity of the individual antigens for detecting antibodies ranged from 21.5% to 67.0%, with 74.3-98.0% specificity. The sensitivity of MPT32 was higher than that of 38KD at a high level of specificity. The six-antigen combination reached a sensitivity of 69.6% in bacterium-negative TB patients, with 77.0% specificity.
Conclusion: The combination panel had markedly improved sensitivity, but specificity requires further enhancement.