Adjusted T SPOT.TB Criteria Can Increase the Specificity of Diagnosis When Differentiating Spinal Tuberculosis From Other Spinal Infections

Abstract Background: The ability of T-SPOT.TB to differentiate Mycobacterium tuberculosis infection of the spine from other infections is little known. This study quantified the efficiency, sensitivity, and specificity of the T-SPOT.TB assay to distinguish between spinal tuberculosis (STB) caused by M. tuberculosis and other infections of the spine and evaluated whether diagnostic performance was improved by adjusting the T-SPOT.TB assay criteria. Methods: From January 2010 to May 2020, 147 patients with spinal infections were recruited. Peripheral blood mononuclear cells were collected, and the number of spot-forming cells was observed. Patients’ white blood cell (WBC) counts, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), procalcitonin (PCT), and TB antibodies were recorded. Specimen/tissue bacteriological culture was the reference standard for sensitivity and specificity. Results: There were 77 (52.4%) participants with confirmed TB and 70 (47.6%) with other infections. The groups were comparable in T-SPOT.TB assay results, age, sex, lesions in the segments, WBC count, CRP, procalcitonin, ESR, and TB antibodies. The sensitivity and specificity of the T-SPOT.TB assay for identifying STB was 88.3% and 40.0%, respectively. On the basis of Relative operating characteristic curve (ROC) analysis and the Youden index, when we adjusted the T-SPOT.TB assay’s diagnostic criteria, ESAT-6>12 or CFP-10>19,the sensitivity and specificity of the T-SPOT.TB assay for identifying STB was 83.1% and 64.3%, respectively. Conclusion: The T-SPOT.TB assay has great sensitivity to distinguish STB from other spinal infections; however, the specificity is extremely low. Specificity can be significantly improved while sensitivity is guaranteed by adjusting the diagnostic criteria.