Sensitivity of human gamma interferon assay and tuberculin skin testing for detecting infection with Mycobacterium tuberculosis in patients with culture positive tuberculosis

Setting: Nine university-affiliated chest clinics in Australia. Objective: To evaluate the sensitivity of a whole blood human gamma-interferon assay (HGIA, QuantiFERON(®)-TB) for specific T lymphocyte responses and Tuberculin skin testing (TST) for the detection of Mycobacterium tuberculosis infection in subjects with culture-proven M. tuberculosis disease (TBCP). Design: Prospective testing of 129 patients with recent TBCP and 100 patients with non-tuberculosis lung disease (NTBLD). Results: Using a defined level of specific IFN-γ production and TST ≥ 10mm as positive cut-offs, the sensitivity of HGIA was 81% compared to 89% for TST (p = 0.06). When positive responses in both TST and HGIA were combined, 96% of TB patients were detected., For the NTBLD group, 43% of whom were born overseas, 73% were negative for both the HGIA and TST. Prior immunization with M. bovis (bacille Calmette-Guerin) (BCG) or the type of TB had no. effect on the sensitivities of the assays. For those treated for < 2 months, the sensitivities for both assays were 84%, but for those treated for > 2 months the sensitivity of TST (90%) tended to be higher than for HGIA (81%) (p = 0.07). The distribution of TST results in TB patients showed a broad peak between 10 and 25 mm, while the results in the HGIA were bimodal in both TB and NTBLD patients. Conclusion: HGIA may prove an alternative to skin testing for detecting A tuberculosis infection in certain settings. © 2004 Elsevier Ltd. All rights reserved.