Clinical utilization of multiple antibodies of Mycobacterium tuberculosis for serodiagnosis evaluation of tuberculosis: a retrospective observational cohort study

OBJECTIVES: We aimed to investigate clinical uncertainties by characterizing the accuracy and utility of commercially available antibodies of Mycobacterium tuberculosis in the diagnostic assessment of suspected tuberculosis in high-burden countries. METHODS: We conducted a retrospective, descriptive, cohort study among participants aged ≥ 18 years with suspected tuberculosis in Nanning, Guangxi, and China. Participants were tested for M. tuberculosis infection using commercially available antibodies against Mycobacterum tuberculosis. Specificity, sensitivity, negative and positive predictive values, and negative and positive likelihood ratios of the tests were determined. Sputum specimens and bronchoalveolar lavage fluid were sent for mycobacterial culture, Xpert MTB/RIF assay, and cell-free M. tuberculosis DNA or RNA assay. Blood samples were used for IGRAs, T-cell counts (CD3 + CD4+ and CD3 + CD8+), and antibodies to tuberculosis test. RESULTS: Of the 1857 participants enrolled in this study, 1772 were included in the analyses, among which, 1311 were diagnosed with active tuberculosis. The specificity of antibody against 16kD for active tuberculosis was 92.7% (95% confidence interval [CI]: 89.3–95.4) with a positive likelihood ratio for active tuberculosis cases of 3.1 (95% CI: 2.1–4.7), which was higher than that of antibody to Rv1636 (90.5% [95% CI: 86.6–93.5]), antibody to 38kD (89.5% [95% CI: 85.5–92.7]), antibody against CFP-10 (82.6% [95% CI: 77.9–86.7]), and antibody against LAM (79.3% [95% CI: 74.3–83.7]). Sensitivity ranged from 15.8% (95% CI: 13.9–17.9) for antibody against Rv1636 to 32.9% (95% CI: 30.4–35.6) for antibody to LAM. CONCLUSIONS: Commercially available antibodies against to Mycobacterium tuberculosis do not have sufficient sensitivity for the diagnostic evaluation of active tuberculosis. However, antibody against Rv1636 and 16kD may have sufficiently high specificities, high positive likelihood ratios, and correspondingly high positive predictive values to facilitate the rule-in of active tuberculosis.