Performance of the Gen-Probe amplified Mycobacterium tuberculosis direct test in a laboratory that infrequently isolates Mycobacterium tuberculosis

Abstract The performance of the Gen-Probe Mycobacterium tuberculosis direct (MTD) test was assessed in a laboratory whose specimens were derived from a population with a low prevalence (1.3%) of tuberculosis. A total of 339 specimens from 113 patients were included in the study. Nine of 10 MTD positive samples were culture positive (smear positive n = 7; smear negative, n = 1; smear not ordered, n = 2). The 10th MTD-positive sample, which was smear and culture negative, was from a patient whose two other study specimens were smear and culture positive and who had a clinical history consistent with tuberculosis. Prior to and following resolution of discrepant results, the sensitivities and specificities of the MTD test relative to culture were 100 and 99.7% and 100 and 100%, respectively.