COMPARATIVE-EVALUATION OF 2 COMMERCIAL AMPLIFICATION ASSAYS FOR DIRECT-DETECTION OF MYCOBACTERIUM-TUBERCULOSIS COMPLEX IN RESPIRATORY SPECIMENS

Two commercial assays detecting the presence of Mycobacterium tubercul osis complex in clinical specimens by rRNA target amplification (Gen-P robe Amplified M. tuberculosis Direct Test [AMTD]) and PCR (Amplicor) were evaluated, The tests were applied to 327 digested, decontaminated respiratory specimens collected from 236 patients, Results were compa red with those of acid-fast staining and culture, The combination of c ulture and clinical diagnosis was considered the ''gold standard.'' A total of 60 specimens were collected from 27 patients with a diagnosis of pulmonary tuberculosis, Thirteen of these specimens were from pati ents receiving standard antituberculosis therapy and therefore were no t included in the comparison, Of the remaining 47 specimens, 33 were s mear positive, 40 were culture positive, 45 were AMTD positive, and 39 were Amplicor positive, After resolution of discrepant results, the o verall sensitivities, specificities, and positive and negative predict ive values were 77, 100, 100, and 95 for staining; 87, 100, 100, and 9 7.4 for culture; 95.9, 98.9, 94, and 99.2 for AMTD; and 85.4, 99.6, 97 .9, and 97.1 for Amplicor, respectively, Agreement between AMTD and Am plicor assay results was 96.8%, It is concluded that although both nuc leic acid amplification methods are rapid and specific for the detecti on of M. tuberculosis complex in respiratory specimens, AMTD appeared to be more sensitive than Amplicor.