EVALUATION OF GEN-PROBE AMPLIFIED MYCOBACTERIUM-TUBERCULOSIS DIRECT TEST AND ROCHE PCR-MICROWELL PLATE HYBRIDIZATION METHOD (AMPLICOR MYCOBACTERIUM) FOR DIRECT-DETECTION OF MYCOBACTERIA

We evaluated the clinical utility of an rRNA amplification-based Gen-P robe Amplified Mycobacterium Tuberculosis Direct Test (AMTD) system an d a PCR-based Roche AMPLICOR MYCOBACTERIUM? system for direct detectio n of Mycobacterium tuberculosis, M. avium, and M. intracellulare. Of t he 422 sputum samples from 170 patients, 137 (121 of M. tuberculosis, 14 of M. avium-M. intracellulare complex [MAC], 2 of mycobacterium oth er than M. tuberculosis or MAC) were culture positive with the Septi-C hek AFB system. One sample of a contaminated culture result was exclud ed for further analyses. The AMTD system detected all of the 121 sampl es which grew M. tuberculosis (sensitivity, 100%). Of the 284 culture negative samples, 28 were positive by this system (specificity, 90.1%) . After resolution of the discrepant samples, based on a positive hist ory for culture of the patient, the specificity of this system increas ed to 99.3%. On the other. hand, the AMPLICOR system gave a positive r esult for 132 out of the 135 culture positive samples for M. tuberculo sis or MAC (sensitivity, 97.8%). Of the 284 culture-negative samples, 37 were positive by this system (specificity, 87.0%). The specificity for this system after resolution of the discrepant samples increased t o 98.9%. The agreement between the results from the AMTD system and th e AMPLICOR system was 98.7%. Both of the systems are highly sensitive and specific for detecting M. tuberculosis and/or MAC directly from sp utum samples within hours, and they should be recommended for routine use in the clinical microbiology laboratory.