Abstract

SA.06.05

Tuberculosis: Etiology of unclear uveitis in the western world

Narsing A. Rao, MD
Doheny Eye Institute, Los Angeles, California, USA

Objective: Diagnosis of uveitis caused by Mycobacterium tuberculosis (TB) is a challenge in western world due to low incidence of systemic tuberculosis and low suspicious index of ophthalmologists and uveitis experts. More over the tuberculous intraocular inflammation can present in the absence of clinical evidence of pulmonary or extrapulmonary disease. A systemic approach in the etiologic diagnosis of intraocular inflammation will circumvent some of the challenges in arriving at proper diagnosis of tuberculous uveitis.
Methods: Patients with chronic uveitis seen in Los Angeles area were investigated with tuberculin skin test (PPD), Gamma interferon release assay, chest X-ray, aqueous humor quantitative polymerase chain reaction (qPCR) to detect TB DNA and response to anti-tuberculosis agents.
Results: The tuberculin skin test and the interferon release assay were helpful in further evaluation of the patients with positive test results but they could not distinguish active tuberculosis of the eye from latent systemic tuberculous infection. Chest X-ray was not helpful in the diagnosis; several patients with qPCR supported diagnosis of intraocular tuberculosis had negative chest X-ray findings. The PCR was also suboptimal in the diagnosis. However therapeutic response to anti-TB agents in PPD positive patients was helpful in arriving at the diagnosis of presumed intraocular tuberculosis, particularly in elderly individuals and those migrated to USA from tuberculosis endemic regions.
Conclusions: High index of suspicion for the tuberculous ocular infection is required in the migrant population, elderly individuals and those with positive PPD and or interferon release assay. A therapeutic trial of the anti-TB agents for duration of 6-8 weeks is helpful in diagnosis of the infection as a presumed one or excluding such diagnosis.

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