Incremental diagnostic value of mycobacterium tuberculosis antigen-based skin test for active tuberculosis: a diagnostic accuracy study

BackgroundIn WHO consolidated guidelines on tuberculosis (TB) for TB infection tests, studies to assess the diagnostic association for active TB compared with current infection tests were recommended as one of the priorities for future research. Previous research has indicated some clinical characteristics of Creation Tuberculin Skin Test (C-TST) which were different from Tuberculin Skin Tests (TST).

Based on these new clinical characteristics, the research objective was to evaluate the incremental diagnostic value of C-TST for the diagnosis of active TB under specific conditions, compared with TST.MethodsThis was a retrospective, non-randomized, exploratory diagnostic accuracy study. The incremental diagnostic value of C-TST above a certain cut-off point was evaluated in suspected Pulmonary Tuberculosis (PTB) cases, and was compared with TST, which was conducted in Chongqing between January 2022 and July 2024.ResultsIn 1553 suspected TB participants, 398 were tested using TST or C-TST.

In active PTB cases, the median diameter of C-TST induration or erythema was significantly larger than that of TST induration (W=5173.5, P<0.001). When using the third quartile of C-TST with active TB (34.3 millimeter) as the cut-off point, positive predictive value (PPV) of C-TST for active TB diagnosis was 74.5% (95%CI, 63.8%-85%) which was significantly larger than that of TST (Z=2.46, P=0.014).ConclusionsAt a specific cut-off value, C-TST shows preliminary exploratory potential for indicating active TB among adult suspected PTB cases.

Further external and prospective validation is still warranted to confirm its clinical diagnostic utility.