Line probe assay – best modality for early diagnosis of multidrug resistant tuberculosis

Abstract

Background: The highest percentage of MDRTB patients are found in India. Early diagnosis and treatment of these cases is vital. GeneXpert is widely recommended as the best tool for early diagnosis of Rifampicin resistance. However Isoniazid resistance which is far more prevalent, is not detected by GeneXpert. Line Probe Assay (LPA) is the modality to detect drug resistance to both these drugs. AIMS: To analyse resistance patterns in LPA and thereby formulate the modality of choice for further investigation of sputum smear positive sample. Materials and Methods: 230 simultaneous sputum smear positive samples were sent for line probe assay Genotype MDRTB plus version 1(Hain lifesciences, Germany)between april2015 to September 2015 Results: 230 patients with sputum smear positive results were further analysed. Rifampicin resistance was obtained by rpoB mutation, isoniazid resistance was obtained by inhA & katG mutations.55 (23.6%) were resistant to isoniazid, 45 patients (19.55%) were resistant to rifampin. 30 patients were resistant to both isoniazid and rifampicin (13.95%). Thus, 23.6% patients with isoniazid resistance would be missed had GeneXpert been used as a modality of diagnosis. Further analysis showed KatG mutation to be more common 45(81.8%) compared to InhA 23(41.2%). Conclusion: Line probe assay should be the modality of choice for rapid diagnosis of MDRTB, especially in sputum smear positive patients.