Detection of Mycobacterium avium complex DNA directly in clinical respiratory specimens: opportunities for improved turn-around time and cost savings

We developed, evaluated, and implemented a Taqman multiplex real-time polymerase chain reaction (PCR) assay for the detection of Mycobacterium avium complex (MAC), targeting the 16S-23S rRNA internal transcribed spacer, which we have combined with an existing Mycobacterium tuberculosis complex assay for use directly in clinical respiratory specimens. Evaluation of the performance of this assay for MAC detection included 464 clinical respiratory specimens tested prospectively. This real-time PCR assay was found overall to have a sensitivity of 71.1%, a specificity of 99.5%, a positive predictive value of 98.0%, and a negative predictive value of 90.2% for MAC. The assay provides results prior to the availability of cultured material and identification, most within 24 h of specimen receipt, and may reduce the need to culture MAC-PCR-positive specimens when susceptibility testing is not requested. Additionally, we have found significant cost savings of approximately $21.00 per specimen and staff time reductions of 3.75 h per specimen with implementation of this assay.