ABSTRACT
Introduction: Important reasons for the negligible numbers of laboratories performing characterization of Mycobacteria in resource constrained settings are requirement of biosafety measures, longer turnaround time and laborious nature of tests. A rapid, accurate and simple test for characterization is required. “SD BIOLINE TB Ag MPT 64 Rapid®” is a rapid immunochromatographic test for differentiation of Mycobacteria into M. tuberculosis Complex (MTBC) and nontuberculous mycobacteria (NTM). Aim: To evaluate a commercial assay, SD TB Ag MPT64 Rapid® for characterization of Mycobacteria isolated on Lowenstein Jensen (LJ) medium. Material and methods: 150 non duplicate isolates which were previously characterized as MTBC or NTM based on standard phenotypic characteristics were tested by the commercial assay after blinding. The result of the conventional phenotypic test and the commercial assay was compared. Any discordant result was referred for confirmation by genotypic Mycobacterium CM assay (Hain’s life sciences, Germany). Sensitivity and specificity of the commercial assay was calculated using the results of conventional phenotypic and genotypic tests as gold standard. Results: Phenotypically, 124 isolates were characterized as MTBC and 26 as NTM. The commercial assay gave concordant results for 149 isolates. One MTBC isolate did not demonstrate a band. The sensitivity, specificity, PPV and NPV was 99.19%, 100 %, 100% and 97.3% respectively. The total turnaround time for the rapid assay was 30 minutes compared to a few hours to days for phenotypic and genotypic method. Conclusion: “SD BIOLINE TB Ag MPT 64 Rapid®” is a simple, rapid and reliable test to differentiate MTBC from NTM.