Comparison of genotype MTBDRplus assay for rapid detection of rifampicin and isoniazid resistance with conventional drug susceptibility tests in a tertiary care hospital in India

Abstract

INTRODUCTION: Emergence of drug resistant tuberculosis (TB) has necessitated the development of molecular based rapid diagnostic tests. WHO has approved Genotype MTBDR plus assay for detection of multidrug resistant (MDR) TB. AIMS: To compare the performance of Genotype MTBDR plus assay with conventional drug susceptibility tests. METHODS: Total 200 specimens (respiratory [sputum, bronchial lavage], lymph nodes, pleural fluid) were analysed on smear for AFB by ZN stain and Genotype MTBDR plus assay which was done as per manufacturer9s instructions. Mycobacterium tuberculosis (MTB) cultures were done by radiometric method. Susceptibility tests were done on L.J. medium. RESULTS: 1. Overall concordance of Rifampicin (RMP) and isoniazid (INH) results between Genotype MTBDR plus assay and conventional susceptibility results was 95.45% and 93.18% respectively. 2. Genotype MTBDR plus assay positivity in AFB smear negative and smear positive but MTB culture positive respiratory samples was 82.15% and 100% respectively. CONCLUSIONS: 1. Genotype MTBDR plus assay is sensitive and specific for rapid diagnosis MDR TB . 2. The sensitivity is 100% in AFB smear positive respiratory samples. 3. Even in AFB smear negative pulmonary TB patients, assay is sensitive for diagnosis of MDR TB.