Validation of a rapid tuberculosis PCR assay for detection of MDR-TB patients in Gauteng, South Africa

Abstract

Nucleic acid amplifcation tests offer shorter turnaround times for diagnosis of tuberculosis (TB) and drug resistance of isolates compared to conventional culture methods. The rapid molecular-based multidrug-resistant (MDR)-TB assay, GenoType® MTBDRplus (Hain Lifescience) was evaluated in Gauteng, South Africa, as a pilot investigation to assess its performance for detection of MDR-TB in patients who were at high risk of drug-resistant TB. A total of 945 sputum specimens sequentially received within a period of six weeks from seven hospitals were assessed by MTBDRplus and compared to liquid culture drug susceptibility tests (DST) using the MGIT 960 system (BD Diagnostic Systems) as the ‘gold standard’. Of the 945 specimens processed, 731 had interpretable results from both tests and therefore were included in the analysis. The overall sensitivities of the MTBDRplus in detecting individual resistance to rifampicin (RMP) and isoniazid (INH), as well as MDR were 95.0%, 93.4% and 100%, respectively. The specifcities were 99.7% for RMP, and 100% for INH and MDR. The Genotype® MTBDRplus assay showed excellent concordance with the conventional ‘gold standard’ MGIT DST, and it detected all the MDR-TB cases analysed.