Prospective Head-to-Head Study Comparing 2 Commercial Interferon Gamma Release Assays for the Diagnosis of Tuberculous Uveitis

Abstract

To perform a head-to-head comparison of 2 commercially available interferon-gamma release assays, QuantiFERON-TB Gold In-Tube (Cellestis, Chadstone, Victoria, Australia) and T-SPOT.TB (Oxford Immunotech, Abingdon, Oxfordshire, UK), in the diagnosis of tuberculous uveitis. Prospective cohort to study diagnostic accuracy. We recruited consecutive new patients who presented with uveitis to a tertiary institution over a 2-year period. All patients underwent complete ocular examination and systemic evaluation, including T-SPOT.TB, QuantiFERON-TB Gold In-Tube, and tuberculin skin test. Patients were followed-up for a minimum of 1 year after completion of antituberculous therapy where indicated. The main outcome measures were the sensitivity, specificity and accuracy of each test, estimated using Bayesian latent class analysis (presented with 95% Bayesian credible intervals) (Crl). Prior information was obtained from published meta-analyses for diagnostic tests: QuantiFERON Gold In-Tube sensitivity (0.64, 0.59-0.69) and specificity (0.99, 0.99-1.00); T-SPOT. tuberculosis sensitivity (0.50, 0.33-0.67) and specificity (0.91, 0.88-0.93). From our study in patients with uveitis, QuantiFERON-TB Gold In-Tube was more specific but slightly less sensitive (sensitivity: 0.64, 0.60-0.69; specificity: 0.995, 0.988-0.999) than T-SPOT.TB (sensitivity: 0.67, 0.60-0.74; specificity: 0.91, 0.88-0.93). However, QuantiFERON Gold In-Tube was significantly more accurate in identifying true-positive tuberculous uveitis cases than was T-SPOT.TB among discordant cases (QuantiFERON Gold In-Tube positive 98% vs T-SPOT.TB positive 76%; ratio 1.28, 95% Crl: 1.11-1.72, ie, 95% Crl >1.0, statistically significant). Based on statistical decision theory, our head-to-head study suggests that QuantiFERON-TB Gold In-Tube is the first-line test that should be performed in preference to T-SPOT.TB (and the tuberculin skin test) for diagnosing tuberculous uveitis.