Diagnostic performance of whole-genome sequencing for identifying drug-resistant TB in Thailand

BACKGROUND: Whole-genome sequencing (WGS) is a promising tool for the detection of drug-resistant TB (DR-TB). To date, there have been few comparisons of diagnostic performance of WGS and phenotypic drug susceptibility testing (DST) in DR-TB.METHODS: We compared drug resistance-conferring mutations identified by WGS analysis using TB-Profiler and Mykrobe with phenotypic DST profiles based on the Löwenstein-Jensen proportion method using drug-resistant Mycobacterium tuberculosis (n = 537) isolates from across Thailand. Based on available phenotypic DST results, diagnostic performance was analysed for resistance against isoniazid, rifampicin, ethambutol (EMB), streptomycin, ethionamide (ETH), kanamycin, capreomycin (CPM), para-aminosalicylic acid, ofloxacin and levofloxacin.RESULTS: High agreement between the two methods was observed for most drugs (>91%), except EMB (57%, 95% CI 53-61) and ETH (70%, 95% CI 66-74). Also, low specificity was observed for EMB (49%, 95% CI 44-54) and ETH (66%, 95% CI 61-71). Sensitivity was high for most drugs (range 83-98%), except CPM (77%, 95% CI 59-88).CONCLUSION: Low agreement between WGS and phenotypic tests for drug resistance was found for EMB and ETH. The current genomic database is insufficient for the identification of CPM resistance. Challenges remain for routine usage of WGS-based DST, especially for second-line anti-TB drugs.