The ability to rapidly distinguish between the Mycobacterium tuberculosis complex (MTC) and nontuberculous mycobacteria (NTM) is critical in clinical practice.
To evaluate the usefulness of an immunochromatographic (IC) assay to distinguish between MTC and NTM.
We analyzed a panel of 145 cultures from 128 patients. Routine molecular identification approaches, such as the AccuProbe™ Mycobacterium tuberculosis complex culture identification test and GenoType(®) Mycobacterium assays, were used as reference methods.
Of the 101 positive cultures, 98 were correctly identified with the Capilia™ TB-Neo assay. Of the three discordant isolates, one was identified as M. Bovis bacilli Calmette-Guérin (BCG) and two as M. tuberculosis. Although we have not performed the sequencing of these strains, some false negatives have been reported due to mutations in the mpb64 gene or with some M. Bovis BCG strains. We did not observe false-positive results or cross-reactions with 22 MNT strains, 12 non-mycobacterial organisms, and 10 negative cultures.
We report good overall performance (97% sensitivity, 100% specificity, 100% positive predictive value, and 96% negative predictive value) of this rapid assay that is easy to perform and interpret and requires no sample preparation, trained technicians, or expensive equipment.