Multigene Mycobacterium tuberculosis cell-free DNA assay

Existing TB diagnostic tests rely on sputum samples, which can be difficult to collect from all patients. This study examines plasma Mycobacterium tuberculosis cell-free DNA (Mtb cfDNA) based quantitative PCR (qPCR) assay for the diagnosis of pulmonary TB (PTB).The qPCR assay targeted insertion sequence (IS6110), cyp141, and devR genes on plasma samples from 106 PTB patients and 60 controls. Sensitivity was calculated using the Xpert^® MTB/RIF test, culture, and clinical diagnosis for the PTB group, while specificity was determined based on results from controls.Among PTB cases, 92 (86.8%) were bacteriologically confirmed, with the remaining 14 (13.2%) diagnosed clinically. The sensitivity of the plasma Mtb cfDNA assay, considering all three genes, was 71.7% (95% CI 62.6-71.7) for all PTB cases, with higher sensitivity in bacteriologically confirmed cases (78.3%) than in clinically diagnosed cases (28.6%). The combined specificity was 91.7%. The combination of IS6110 and cyp141 targeted qPCR demonstrated a sensitivity of 70.8%, and IS6110 and devR showed a sensitivity of 69.8%. However, devR and cyp141 resulted in a lower sensitivity of 63.2%. IS6110 and cyp141 had sensitivities of respectively 59.4% and 60.4%, while devR had 53.8%.Targeting multiple genes for plasma Mtb cfDNA-based TB diagnosis improves sensitivity and could be an important addition to current sputum-based diagnostic approaches..