Diagnostic efficacy of polymerase chain reaction in granulomatous uveitis

The granulomatous uveitis, multifocal choroiditis and periphlebitis have been suspected to be of tubercular origin but no definitive reports about detection of etiological agents have been documented in the literature. Conventional bacteriological methods are not generally helpful in diagnosing ocular tuberculosis due to difficulty with potential morbidity associated with obtaining the biopsy material from the eye. Thus, the diagnosis of ocular tuberculosis is most often presumptive.

We evaluated the role of polymerase chain reaction (PCR) for detection of Mycobacterium tuberculosis in the aqueous humor samples obtained from eyes with active uveitis.

Aqueous samples from 53 patients having cellular reaction in the anterior chamber along with any one or more of the following: 1) active vasculitis; 2) anterior vitreous cells; 3) snowball opacities; 4) snow banking in the pars plana; 5) retinochoroiditis were withdrawn by anterior chamber paracentesis and subjected to PCR. Seventeen samples from patients with definite clinical diagnoses other than tuberculosis formed a disease control group. Fifteen aqueous samples obtained from healthy subjects undergoing routine cataract surgery served as healthy controls. PCR was performed using primers capable of amplifying a 150 b.p. segment from a conserved repetitive sequence in the genome of M. tuberculosis.

Twenty out of the 53 samples (37.7%) in the study group were positive where as only one sample out of 17 in the disease control group (5.7%) showed a weakly positive band. No sample from the healthy control group showed a positive PCR.

Our study shows that PCR can be effectively used for the diagnosis of intraocular tuberculosis in the presence of uveitis.