Validation of a Rapid Tuberculosis PCR Assay for Detection of MDR-TB Patients in Gauteng; South Africa

ABSTRACT

Nucleic acid amplification 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; GenoTyper 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; 93.4and 100; respectively. The specificities were 99.7for RMP; and 100for INH and MDR. The Genotyper MTBDRplus assay showed excellent concordance with the conventional `gold standard' MGIT DST; and it detected all the MDR-TB cases analysed