Utility of QuantiFERON®-TB Gold test in diagnosis and management of suspected tubercular uveitis in India

Abstract

The tuberculin skin test, used to detect latent systemic tuberculosis (TB), has its limitations. The utility of interferon-gamma assays, found useful in the diagnosis of latent TB, is still unestablished in tubercular uveitis. We present the results of QuantiFERON(®)-TB Gold (QFT-G) test and its relevance in the diagnosis and management of suspected tubercular uveitis in India. All suspected tubercular uveitis patients seen at our uveitis clinic between October 2006 and June 2008 who underwent relevant blood investigations, chest X-rays, Mantoux tests and QFT-G tests were included. Clinical profile, systemic correlation and outcome with treatment were analysed. Fifty suspected tubercular uveitis patients underwent QFT-G testing. The age range of the patients was 6-55 years (mean 32.66 years). Seven patients presented with active and three with a past history of systemic TB. The QFT-G test was positive in 29 patients. Radiological findings of TB were seen in four patients with a positive QFT-G and one patient with a negative QFT-G test. In 11 patients both QFT-G and Mantoux tests were positive. Eighteen Mantoux-negative patients were QFT-G-positive. Significantly, no patient with a positive Mantoux had a negative QFT-G test. Of the 32 patients with posterior uveitis, 17 patients had serpiginous choroiditis, four patients had a choroidal granuloma, six patients had multifocal choroiditis, four patients had retinal vasculitis, and one patient had a subretinal abscess. All QFT-G-positive patients were treated with anti-tuberculosis therapy as well as systemic steroids with a favorable clinical outcome. Our study shows that the QFT-G test is very useful in the diagnosis and management of suspected ocular TB. It was found to be very sensitive in identifying latent TB patients who, upon treatment, had a significantly reduced frequency of recurrences. It was more sensitive than the Mantoux test and is not significantly affected by previous treatment with systemic steroids or immunosuppressives. A negative QFT-G test can also be used as an adjunct before initiation of systemic steroids or immunosuppressives in uveitic patients particularly in an endemic setting like India.