Diagnostic accuracy of interferon-gamma release assay and mucosal-associated invariant T cells in spinal tuberculosis

Conventional diagnostic methods for tuberculous spondylodiscitis (TS) require tissue biopsy, which can delay diagnosis. Immunodiagnostic approaches, including interferon-gamma release assays (IGRAs), have shown potential for improving TS diagnosis. Recent advancements have also identified the potential role of mucosal-associated invariant T (MAIT) cells as biomarkers for TB infection. This study aims to evaluate the diagnostic performance of IGRA using the QuantiFERON-TB Gold In-Tube test (QFT-GIT) and MAIT cell analysis for diagnosing TS. Sixty-five patients suspected TS were prospectively enrolled, of whom 24 (37%) were categorized as confirmed TS. QFT-GIT demonstrated a sensitivity of 82.61% and specificity of 77.78%. No significant differences were found in the proportion of MAIT cells, CD4 + MAIT, CD8 + MAIT, and Double negative (CD4- CD8-) MAIT when compared between TS and non-TS patients. However, The MAIT cell population in CD8 + T lymphocytes subset was significantly higher in patients with TS (p = 0.0081). MAIT cell percentage > 2.63% in CD8 + T cell subset demonstrated fair discriminative ability, with an AUC of 0.746, sensitivity of 90.5%, and specificity of 51.4%. Combining QFT-GIT and the proportion of MAIT cells in CD8 + T cells subset improved specificity to 96.9%. These findings highlight the potential of these tests as promising, non-invasive diagnostic tools for differentiating TS in spondylodiscitis patients, especially when tissue diagnosis is not feasible.