Comparison of 2 interferon-gamma assays and Roche Cobas Amplicor Mycobacterium tuberculosis assay for rapid diagnosis of tuberculosis among patients with suspected tuberculosis in Taiwan.

摘要

BACKGROUND AND PURPOSE: Two commercial interferon-gamma (IFN-gamma) assays, which are commonly used for diagnosing latent tuberculosis (TB), are also useful for diagnosis of active TB. In this study, the IFN-gamma assays and polymerase chain reaction (PCR) for diagnosis of TB were compared. METHODS: A prospective comparison of the performance of 2 commercial IFN-gamma assays - QuantiFERON-TB Gold (QFT-G) and T-SPOT.TB (T SPOT) - and PCR using the Roche Cobas Amplicor Mycobacterium tuberculosis (RCA-TB) assay for the rapid diagnosis of TB was conducted from January 2007 to December 2007 at a university-affiliated hospital in Taiwan. RESULTS: Of 187 patients enrolled in the study, results from both T SPOT and QFT-G were available for 154, including 109 patients with active TB and 45 with no TB. The sensitivity of T SPOT (89.0%) was higher than that of QFT-G (71.4%). RCA-TB had the highest sensitivity (90.2%) and specificity (100%), but was usually performed in patients with positive acid-fast bacilli smear test. In patients with extrapulmonary TB, T SPOT had a high diagnostic value (sensitivity, 81.3%). A significant discordance between the 2 IFN-gamma assays was also noted. IFN-gamma assays provided a more rapid diagnosis for tuberculosis than the conventional culture method (mean +/- standard deviation, 8.23 +/- 12.86 days; p < 0.001). CONCLUSIONS: Use of IFN-gamma may shorten the time to diagnosis of TB, especially for smear-negative patients and those with extrapulmonary disease.