Usefulness of an in-vitro tuberculosis interferon-γ release assay (T-SPOT.TB) in the first-line check-up of uveitis patients

Objectives. The main objective of this 1.5-year prospective study was to evaluate the value of T-SPOT<SU (R)</SU.TB as compared to the tuberculin skin test (TST) for the first-line assessment of uveitis. Methods. A total of 108 consecutive non-immunocompromised patients with acute or chronic uveitis, including 92/108 (85.2%) with previous BCG vaccination, underwent a general examination, a TST, and a T-SPOT.TB test (Oxford Immunotec; Oxford, UK), blood and serological tests, and chest imaging. Concordance between tests was assessed using kappa coefficients. The performance of binary classification tests was evaluated with sensitivity, specificity, and likelihood ratios. Results. The results of the TST and the T-SPOT.TB test differed significantly (55.5% versus 29.6% positivity, P < 0.001), with a low concordance between the two tests (kappa = 0.362, P = 0.001). The sensitivity of the TST was 100% (diagnosis of suspected tuberculous uveitis included a positive TST), but its specificity was only 53.3%. The sensitivity and the specificity of the T-SPOT.TB test were 94.4% and 83.3%, respectively. The positive and negative likelihood ratios of the T-SPOT.TB test were 5.67 and 0.07, respectively. Conclusion. In uveitis patients with frequent previous BCG vaccination, the T-SPOT.TB test is more specific than the TST and therefore allows more accurate selection of patients requiring extensive investigations to rule out TB diagnosis.