Use of an immunochromatographic assay for rapid identification of <i>Mycobacterium tuberculosis</i> complex clinical isolates in routine diagnosis

Accurate identification of Mycobacterium tuberculosis complex (MTBC) isolates is essential for tuberculosis (TB) control, especially in a high-burden country such as Brazil. Conventional identification methods are laborious and time-consuming, while rapid molecular methods are expensive and require skilled personnel and appropriate physical laboratory infrastructure. Immunochromatographic assays (ICAs) have been shown to provide a rapid and reliable TB diagnosis at a low cost. The use of the SD Bioline TB Ag MPT64 ICA (MPT64 assay) for rapid identification of MTBC clinical isolates in the routine diagnosis of a large-volume reference TB laboratory was evaluated. We analysed 375 isolates on solid and liquid media concurrently with conventional phenotypic methods, the PRA- hsp 65 molecular technique and the MPT64 assay. The sensitivity, specificity and accuracy of the ICA were 97.7, 100 and 98.1 %, respectively. The MPT64 assay yielded rapid and accurate results, enabling the treatment to be initiated early and also impacting on TB control.