Performance of the Genotype (R) MTBDRPlus assay in the diagnosis of tuberculosis and drug resistance in Samara, Russian Federation

Background: Russia is a high tuberculosis (TB) burden country with a high prevalence of multidrug resistant tuberculosis (MDRTB). Molecular assays for detection of MDRTB on clinical specimens are not widely available in Russia. Results: We performed an evaluation of the GenoType (R) MTBDRplus assay (HAIN Lifescience GmbH, Germany) on a total of 168 sputum specimens from individual patients at a public health laboratory in Central Russia, as a model of a middle income site in a region with high levels of drug resistance. Phenotypic drug resistance tests (DST) were performed on cultures derived from the same sputum specimens using the BACTEC 960 liquid media system. Interpretable GenoType (R) MTBDRplus results were obtained for 154(91.7%) specimens with readability rates significantly higher in sputum specimens graded 2+ and 3+ compared to 1+ (RR = 1.17 95% CI 1.04-1.32). The sensitivity and specificity of the assay for the detection of rifampicin (RIF) and isoniazid (INH) resistance and MDR was 96.2%, 97.4%, 97.1% and 90.7%, 83.3%, 88.9% respectively. Mutations in codon 531 of the rpoB gene and codon 315 of the katG gene dominated in RIF and INH resistant strains respectively. Disagreements between phenotypical and molecular tests results (12 samples) could be explained by the presence of rare mutations in strains circulating in Russia and simultaneous presence of resistant and sensitive bacilli in sputum specimens (heteroresistance). Conclusion: High sensitivity, short turnaround times and the potential for screening large numbers of specimens rapidly, make the GenoType (R) MTBDRplus assay suitable as a first-line screening assay for drug resistant TB.