The utility of routine tuberculosis screening in county hospital patients with uveitis

Background/aim: To evaluate the utility of tuberculosis (TB) screening in diagnosing ocular TB in uveitis patients in a government-funded hospital. Methods: The charts of 142 consecutive patients seen during August 2011-July 2012 at the Los Angeles County Hospital uveitis clinic were reviewed for manifestation/laterality of uveitis, purified protein derivative (PPD) test results, interferon γ release assay, chest x-ray, birthplace, treatment history and diagnosis. 'Presumed TB-uveitis' was diagnosed when patients had positive TB screening and favourable response to anti-TB therapy, and de finite ocular TB when Mycobacterium tuberculosis ' presence was demonstrated. Post-test probabilities were determined. Results: TB screening was positive in 21.1%. Six patients were diagnosed with TB-related uveitis: one definite, four presumed and one systemic TB with uveitis. With regard to PPD positivity, being foreign-born was the only statistically significant factor with OR of 2.26 (95% CI 1.01 to 5.13; p<0.01) if born in Mexico and 4.90 (95% CI 1.74 to 13.83; p<0.01) if born in other foreign countries. The post-test probabilities of a positive PPD in a uveitis patient showed a 17.2% (overall) or 30.3% (foreign-born patients) chance of ocular TB. Conclusions: PPD skin test plays an important role in the diagnosis of TB-associated uveitis in high-risk groups, such as immigrants from TB endemic regions.