Improved diagnosis of tuberculosis in HIV-positive patients using RD1-encoded antigen CFP-10

Summary Objective The present study was aimed at determining the serodiagnostic potential of 38-kDa (Rv0934, Mycobacterium tuberculosis complex-specific antigen) and CFP-10 (Rv3874, RD1 antigen) antigens among HIV-positive and HIV-negative patients with pulmonary TB. Methods The diagnostic potential of native 38-kDa (n38-kDa) and recombinant CFP-10 (rCFP-10) antigens was ascertained in terms of sensitivity and specificity using an indirect ELISA. The study included 508 HIV-seronegative TB patients (TB), 54 HIV-seropositive TB patients (HIV–TB), 30 HIV-positive patients without TB (HIV), and 256 controls. Results In HIV–TB, the sensitivities for individual antigens ranged from 14.8% to 31.5% and the specificity was >98% for IgG. When IgA results were added to IgG, the sensitivity increased to 25.9% for 38-kDa and 57.4% for CFP-10; specificity changed to 97.5% for 38-kDa and 98.1% for CFP-10. The combined results of both the antigens gave 59.3% sensitivity and 95.6% specificity. In TB, the sensitivity was 82.8% when the antigen results were combined. None of the HIV-infected controls showed positivity for IgG to either of the two antigens. Conclusion Use of CFP-10 enhances the sensitivity of 38-kDa, and therefore the 38-kDa and CFP-10 antigen combination can be a diagnostic marker in HIV–TB

Evaluation of the diagnostic potential of region of deletion-1–encoded antigen culture filtrate protein-10 in pulmonary tuberculosis

The ability of region of deletion-1 (RD-1)–encoded culture filtrate protein-10 (CFP-10) to supplement the sensitivity of 38-kDa antigen was studied using enzyme-linked immunosorbent assay in pulmonary tuberculosis (TB) patients and controls. The sensitivities for individual antigens ranged from 50% to 60%, and the specificity was 100% for immunoglobulin (Ig) G alone. When IgA results were added to IgG, the sensitivity increased. On combination of the isotype results, sensitivity increased to 61.8% and 57.2% (for 38-kDa antigen and CFP-10), respectively, and specificity changed to 98.8% and 99.4% for 38-kDa and CFP-10, respectively. Combination of results of both the antigens gave 82.4% sensitivity in smear-positive and culture-positive group, and 98.1% specificity. In smear-negative and culture-positive group, the sensitivity was 66.7%. In smear-negative and culture-negative cases, a sensitivity of 65.6% was obtained. This study demonstrates that the use of RD-1–encoded CFP-10 enhances the sensitivity of 38-kDa antigen and can be a useful diagnostic marker in TB