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®.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 (κ = 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.