Gamma interferon assay as an alternative to PPD skin testing in selected patients with granulomatous intraocular inflammatory disease

Background: To evaluate the QuantiFERON-TB test (gamma interferon assay), approved by the Centers for Disease Control and Prevention for the detection of latent tuberculosis (LTB), in patients who potentially may require immunosuppressive therapy for ocular inflammatory disease. Methods: Blood samples from 12 consecutive patients with granulomatous ocular inflammatory disease were evaluated first with the purified protein derivative (PPD) skin test and then with the QuantiFERON-TB test (I I of 12 patients, I declined). The results of the 2 tests in both U.S.- and non-U.S.-born patients were compared with their Bacillus Calmette-Guerin (BCG) vaccination status and chest x-rays. Results: In our small series there was a high degree of concordance between the QuantiFERON-TB assay and the PPD skin test. Interpretation: The QuantiFERON-TB test did not demonstrate intrinsic merit over IPPD skin testing for screening for LTB in selected patients when immunosuppressive therapy is considered. The confounding effect of BCG vaccination renders interpretation of both tests difficult. Early reports suggest the second-generation tests that are now available may hold promise for use in the uveitis clinic and should be formally evaluated.