Accuracy of Tuberculosis Infection Diagnosis through IP-10-Based Assays for Immune Detection of Present Mycobacterium tuberculosis: A Cross-Sectional Evaluation

BackgroundReliable detection of latent Mycobacterium tuberculosis (Mtb) infection (LTBI) remains challenging, particularly in TB contacts and immunocompromised individuals, where interferon-{gamma} release assays (IGRAs) demonstrate variable sensitivity. IP-10, a chemokine produced at substantially higher concentrations than IFN-{gamma}, represents a promising immune marker. This study aimed to evaluate the diagnostic performance of two IP-10 based assays RIDA(R)QUICK TB (lateral flow) and RIDASCREEN(R) TB (ELISA), by comparison with QuantiFERON-TB Gold Plus (QFT-Plus) assay or a composite reference standard. MethodsA cross-sectional diagnostic accuracy study enrolled 99 adults: 49 with culture-confirmed active pulmonary TB, 30 close TB contacts and 20 individuals with autoimmune disease, in Bucharest, Romania. All participants underwent RIDA Quick, RIDA Screen and QFT-Plus testing. Indeterminate results for all assays were reclassified using a composite reference standard. ResultsAgainst culture in active TB cases, RIDA(R)QUICK TB demonstrated a sensitivity of 85.7% (95% CI: 72.8-94.1) and PPV of 97.7%, while RIDA(R)SCREEN TB achieved 91.8% sensitivity (95% CI: 80.4-97.7) and 97.8% PPV. Specificity and NPV could not be reliably estimated due to the near-absence of true-negative individuals. Agreement with QFT-Plus was moderate to good ({kappa}=0.47-0.93).ROC analysis performed against QFT-Plus as a comparator demonstrated good immunological discrimination for RIDA(R)QUICK TB (AUC = 0.828) and RIDA(R)SCREEN TB (AUC = 0.767), reflecting concordance with QFT-Plus rather than diagnostic accuracy against confirmed infection. ConclusionIP-10 based assays demonstrated higher sensitivity than QFT-Plus and excellent PPV across bacteriological standard, supporting their use as complementary tools for LTBI detection. Larger, more heterogeneous cohorts are needed to accurately define specificity and operational integration.