Evaluation of the GenoType MTBDRplus v2 Line Probe Assay for Rapid Diagnosis of Multidrug Resistant Tuberculosis in Uganda

Abstract

Introduction: Multidrug-resistant tuberculosis (MDR-TB) poses a major challenge to TB control due to its complex diagnostic and treatment challenges. Globally, 3.7% of new cases and 20% of previously treated cases are estimated to have MDR-TB (1). In 2010, only 18% of the estimated MDR-TB patients were reported to have been diagnosed as a result of serious laboratory capacity constraints (3). Currently there is only one line probe assay, GenoType® MTBDRplus (Hain Lifescience GmBH, Nehren, Germany) which was endorsed by WHO for the rapid detection of MDR TB. In 2011, Hain Lifescience came up with a newer version of LPA called GenoType® MTBDRplus version 2 (or Hain v2) which seem to be superior to version 1 though scanty data is available to support this in the Ugandan setting. Aim: This study intended to evaluate the performance of MTBDRplus v2 assay for the rapid detection of MDR-TB in Uganda and provide more data for performance review of the test. Methods: This was a laboratory based cross sectional study where 126 left over sputum samples were tested using MTBDRplus v2 using MGIT culture and MGIT DST as reference standards. Statistical analysis was performed using Microsoft Excel 2007 (Microsoft Corporation) and STATA 8.0 software (Statacorp LP, College Station, TX, USA). Results: MTBDRplus v2 had a sensitivity of 97.7% and specificity of 40.0% in detecting M. tuberculosis complex (MTBC) using MGIT-culture as a gold standard. Both the sensitivity and specificity of Hain v2 in detecting RIF resistance was 100%. Hain v2 detected INH resistance with a sensitivity of 75.0% and specificity of 96.0%. MTBDRplus v2 gave interpretable RIF and INH results in 46% (29/63) of the smear negative samples compared to 14% to 16% reported when using GenoType MTBDRplus v1 (11). Conclusion: MTBDRplus v2 is a highly sensitive test for detection of Mycobacterium tuberculosis complex and rifampicin resistance. The test produced very high specificities for rifampicin and isoniazid detection. GenoType MTBDRplus v2 should be incorporated in the laboratory workflow to diagnose MDR TB in Uganda irrespective of the sputum smear status.