Combined plasma cell-free DNA detection and IFN-γ/TNF-α dual fluorospot assays for diagnosing active tuberculosis

Abstract Background : Present molecular and microbiologic diagnostic tests have suboptimal sensitivity for diagnosing pauci-bacillary tuberculosis (TB). We recently developed a combined molecular and immunodiagnostic test for active TB involvingdetection of cell-free DNA (cfDNA) and of IFN-γ/TNF-α release from blood. We evaluated the diagnostic performance of this new test from patients with suspected TB. Methods : Adult patients suspected of active TB were prospectively enrolled from March 2019 to September 2021. CfDNA detection and the IFN-γ/TNF-αdual release fluorospot assay were performed using plasma and PBMC specimens. Final diagnosis of patients with suspected TB was provided by clinical category. Results : A total of 105 patients including 54 with active TB and 51 with not-active TB were finally analyzed. The sensitivity and specificity of cfDNA detection in plasma were 67% (95% CI, 53–79) and 80% (69–92), respectively, and those of the IFN-γ/TNF-αdual release fluorospot assay of PBMCs were 80% (67–89) and 90% (79–97), respectively. The sensitivity and specificity of the combined assays were 91% (80–97) and 77% (63–87). Conclusion : The combination of cfDNA detection and the IFN-γ/TNF-αdual release assay using blood specimens appears to be a useful adjunct test for the diagnosis of active TB.