Comparison of two interferon gamma release assays (IGRA) for tuberculous uveitis
Reviewed by Efrosini Papagiannuli

In this prospective cohort study the authors compared QuantiFERON-TB Gold In-Tube and T-SPOT.TB to evaluate their diagnostic accuracy. They enrolled 120 consecutive new uveitis presentations over a two year period in a tertiary centre. The majority were Chinese (61.3%), followed by Indian (20.8%) and Malay (6.6%). In total, 106/120 patients completed the follow-up for at least one year after completion of ocular and systemic treatment (including TB treatment where necessary); 43.4% presented with bilateral uveitis, 59.9% anterior, 2.6% intermediate and 15.1% posterior uveitis. 22.4% had panuveitis. The clinical signs suggesting possible underlying TB ranged from granulomatous inflammation in 25%, extensive posterior synechiae in 19.1%, vasculitis in 12.5% to serpiginous choroiditis in 0.7% (one patient). One patient had mycobacterium positive sputum sample and another patient had a positive urine sample (with a positive skin test and negative IGRA). All patients underwent ocular and systemic examination, baseline blood tests, CXR, Mantoux test, QuantiFERON-TB Gold In-Tube and T-SPOT.TB testing. The main outcome measures were the sensitivity and specificity of each test and their accuracy. The authors performed a meta-analysis of previously published literature on the prevalence of tuberculous uveitis (1987-2008) and found that recorded prevalences ranged from 0.06% (USA) to 10.5% (Saudi Arabia). The Bayesian analysis which was used for evaluation of the tests suggested that, regardless of the endemic prevalence of TB related uveitis, the QuantiFERON-TB Gold In-Tube was more specific but a little less sensitive than T-SPOT.TB and significantly more accurate in identifying tuberculous uveitis. The QuantiFERON-TB Gold In-Tube remained the more superior test after sensitivity analyses and varying the prevalence or probability of tuberculous uveitis. The authors conclude that in the absence of a gold standard test, a combination of any two IGRAs or traditional tests (skin testing), would improve the diagnostic accuracy. However, because of the high cost they recognise that further studies are needed to assess the most cost-effective combination and sequence of tests to assist in the diagnosis of tuberculous uveitis.

Prospective head-to-head study comparing 2 commercial interferon gamma release assays for the diagnosis of tuberculous uveitis.
Ang M, Wong WL, Kiew SY, et al.
AMERICAN JOURNAL OF OPHTHALMOLOGY
2014;157:1306-14