MULTIPLEX PCR ASSAY FOR IMMEDIATE IDENTIFICATION OF THE INFECTING SPECIES IN PATIENTS WITH MYCOBACTERIAL DISEASE

Rapid identification of infecting mycobacterial species enables approp riate medical care decisions to be made. Our aim was to demonstrate th e clinical usefulness of the multiplex PCR assay, a test based on PCR, which permits direct identification of 12 mycobacterial species in cl inical specimens. A total of 259 specimens from 177 patients who had c linical symptoms of mycobacterial disease but for whom there were diff iculties in diagnosis were tested. Specimens were analyzed within 48 h of receipt of the sample. Mycobacteria were identified in 102 specime ns; 66 specimens contained nontuberculous mycobacteria, and 36 specime ns contained Mycobacterium tuberculosis complex mycobacteria. The PCR assay identified the mycobacterial species in 43 (97.7%) of 44 microsc opy- and culture-positive specimens and in 15 (93.8%) of 16 culture-po sitive, microscopy-negative specimens. It also permitted species ident ification in infections caused by more than one mycobacterial species. For 56 (96.5%) of the 58 specimens from patients with infections caus ed by opportunistic mycobacteria, the organisms were identified with t he PCR assay. The test was useful also for the identification of fasti dious mycobacteria, e.g., M. genavense, and those that cannot be cultu red, e.g., M. leprae. After resolution of discrepant results, the sens itivity of the PCR assay was 97.9%, the specificity was 96.9%, the pos itive predictive value was 95.0%, and the negative predictive value wa s 98.7%. For culture these values were 60.8, 100, 100, and 81.0%, resp ectively. Thus, the multiplex PCR assay enables prompt diagnosis when rapid identification of infecting mycobacteria is necessary.