Diagnostic Values of Peripheral Blood T-Cell Spot Test for Tuberculosis (T-SPOT.TB) for Spinal Tuberculosis

The T-cell spot test for tuberculosis (T-SPOT.TB) with false positives and false negatives exists in the diagnosis of spinal infection. The objective of this study was to increase the diagnostic value precision and specificity of T-SPOT.TB in the identification of spinal tuberculosis (TB). Fifty-two patients suspected of having spinal TB from April 2020 to December 2021 were included, and all patients received T-SPOT.TB tests and surgical treatment. The composite reference standard was used to diagnose spinal TB. The T-SPOT.TB values were compared according to whether spinal TB was diagnosed, and the optimal cutoff values of diagnosis was determined by receiver operating characteristic (ROC) curve analysis. All patients were followed up for at least one year. The sensitivity, specificity, positive predictive value, and negative predictive value of the T-SPOT.TB test in assisting the diagnosis of spinal TB were 91.67%, 71.43%, 73.33%, and 90.9%, respectively. We determined that the values of early secreted antigen target 6 (ESAT-6) antigen and culture filter protein 10 (CFP-10) antigen were determined to be diagnostic for spinal tuberculosis, with areas under the curve equal to 0.776 and 0.852, respectively; the cutoff values for the diagnosis of ESAT-6 antigen and CFP-10 antigen were calculated as 40.5 spot forming cells (SFCs) per 10⁶ peripheral blood mononuclear cells (PBMCs) and 26.5 SFCs/10⁶ PBMCs, respectively. Follow-up for all patients was 12 months, and in this period, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), visual analog scale (VAS) score, and Oswestry Dysfunction Index (ODI%) were different between groups (p < 0.05). The T-SPOT.TB test is considered a milestone discovery in the diagnosis of TB; there are still many false-positive samples, but the diagnostic specificity was improved in the study, allowing spinal infections to be treated accurately and in a timely manner.