Diagnostic efficacy of the TSPOT assay for tuberculosis infection and drug resistance in mycobacterium tuberculosis in patients with malignant tumors

Immunosuppression in cancer patients clearly elevates the risk of acquiring tuberculosis (TB) infection, and traditional diagnostic methods are characterized by low sensitivity (Sen) and long turnaround times.Although the interferon-gamma release assay (IGRA) is widely used, its ability to distinguish active tuberculosis (ATB) from latent tuberculosis infection (LTBI) in cancer patients, as well as its relationship with drug resistance (DR), remains unclear.This study aimed to evaluate the diagnostic efficacy of T-SPOT for active tuberculosis and its ability to distinguish active tuberculosis from latent tuberculosis infection in patients with malignant tumors.A retrospective analysis was conducted on data from 634 patients with malignant tumors, and patients were grouped: active tuberculosis (ATB) group (AG, n = 76), LTBI group (BG, n = 184), and non-TB group (CG, n = 374).The interferon-gamma (IFN-) response induced by Early Secreted Antigenic Target 6 (ESAT-6)/Culture Filtrate Protein 10 (CFP-10) was detected by TSPOT, and the relationship between TSPOT and DR was analyzed.Subgroup analysis and multivariate regression were used to explore the immune-related factors affecting the positive rate of TSPOT.The results showed Sen for ATB was 86.8%, and specificity (Spe) was 73.3%.The Sen for screening TB infections was 80.4%, with a Spe of 98.4% and a positive predictive value (PPV) of 97.2%.The Spe for differentiating ATB from LTBI was only 22.3%.The overall DR rate in the AG was 59.2% (45/76), including rifampicin (RIF) resistance (36.8%), multidrug-resistant TB (MDR-TB) (21.1%), and pre-extensively drug-resistant TB (Pre-XDR-TB) (7.9%).The median total spot count of TSPOT in the drug-resistant group was significantly lower than that in the drug-sensitive group [52 (IQR 25-85) vs. 120 (IQR 85-188), P < 0.001], and the spot count showed a decreasing trend as the number of drug-resistant types increased (P < 0.001).Multivariate regression showed that low lymphocyte count (< 0.810 9 /L) and high-dose steroid use (> 40 mg/d) were independent factors associated with a reduced positive rate of TSPOT.In summary, TSPOT is suitable for screening TB infection in patients with malignant tumors but has limited capacity to differentiate ATB from LTBI.The significant reduction in TSPOT spot counts was closely associated with MTB drug resistance and host immunosuppressive status, suggesting that this indicator may serve as an auxiliary early warning tool for drug-resistant tuberculosis.