Setting: Pham Ngoc Thach Tuberculosis Reference Hospital, Ho Chi Minh City, Viet Nam.
Design: A multiplex allele-specific polymerase chain reaction (MAS-PCR) was developed to detect mutations at the two most common sites responsible for isoniazid (INH) resistance in Mycobacterium tuberculosis: katG315 and inhA-15. The MAS-PCR is able to detect rare mutations at katG315, in addition to katG S315T. Conventional phenotypic proportion drug susceptibility testing on Löwenstein-Jensen media was used as a gold standard to compare the sensitivity and specificity of the commercial MTBDRplus line-probe assay and the MAS-PCR in 100 INH-resistant and 50 INH-susceptible isolates collected consecutively at Pham Ngoc Thach Hospital reference laboratory.
Results: The sensitivity and specificity on culture isolates were 90% (n = 90/100, 95%CI 0.83-0.94) and 100% (n = 50/50, 95%CI 0.93-1.0), respectively, for the MAS-PCR and the MTBDRplus assay.
Conclusion: The MAS-PCR described here represents an alternative method for rapid screening for INH resistance in M. tuberculosis isolates.