DETECTION AND IDENTIFICATION OF MYCOBACTERIUM-TUBERCULOSIS DIRECTLY FROM SPUTUM SEDIMENTS BY LIGASE CHAIN-REACTION

Sputum specimens received for the diagnosis of tuberculosis or other m ycobacterial infections were tested by a ligase chain reaction (LCR)-b ased assay and acid-fast stain and culture techniques, Results from th e LCR assay (Abbott LCx Mycobacterium tuberculosis [MTB] Assay) were c ompared to results from standard culture techniques held for 6 weeks, Four hundred ninety-three specimens from 205 patients suspected of pul monary tuberculosis were included in the prospective study, Thirty-fou r (6.9%) of the specimens were culture positive for M. tuberculosis, a nd 13 (38%) of these were also fluorochrome stain positive, LCR sensit ivities and specificities compared to culture were 74 and 98%, respect ively, LCR sensitivity was 100% for fluorochrome stain-positive specim ens and 57% for fluorochrome stain-negative specimens. Nine LCR-negati ve, culture-positive specimens were the result of low concentrations o f M. tuberculosis. No inhibitors were detected in any of these specime ns, Of the eight LCR-positive, culture-negative specimens, five were f rom patients with active tuberculosis, With these considered culture m isses, final LCR sensitivity, specificity, positive predictive value, and negative predictive value were 77, 99, 91, and 98%, respectively, The same performance values for the fluorochrome acid-fast bacillus sm ear were 33, 98, 62, and 94%, respectively, After normal laboratory sp utum processing, the Abbott LCx MTB Assay can be completed in 6 h. Thu s, it is possible to have results available within 8 h of specimen sub mission.