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

Background: 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).Patients and Methods: 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.Results: 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 10(6) peripheral blood mononuclear cells (PBMCs) and 26.5 SFCs/10(6) 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).Conclusions: 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.

Automated summary

This study aimed to improve the diagnostic accuracy and specificity of T-SPOT.TB in spinal tuberculosis (TB) identification. T-SPOT.TB values were compared and optimal cutoff values were determined. The test showed high sensitivity and specificity in assisting the diagnosis of spinal TB. During follow-up, there were differences in CRP, ESR, VAS score, and ODI% between groups.