Capilia™ TB-Neo assay: a new tool for rapid distinction between tuberculous and non-tuberculous mycobacteria

The ability to rapidly distinguish between Mycobacterium tuberculosis complex (MTC) and non-tuberculous mycobacteria (NTM) is critical in clinical practice.

To evaluate the usefulness of an immunochromatographic (IC) assay to distinguish between MTC and NTM.

We analysed a panel of 145 cultures from 128 patients. The 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 using the Capilia™ TB-Neo Assay. Of the three discordant isolates, one was identified as M. bovis bacille Calmette-Guérin (BCG) and two as M. tuberculosis. Although we have not performed the sequencing of these strains, some false-negative results have been described due to mutations in the mpb64 gene or with some M. bovis BCG strains. We did not observe false-positive results or any cross-reaction with 22 NTM strains, 12 non-mycobacterial micro-organisms and 10 negative cultures.

We report good overall performance (sensitivity 97%, specificity 100%, positive predictive value 100% and negative predictive value 96%) of this rapid assay that is easy to perform and interpret and does not require sample preparation, trained technicians or expensive equipment.