Validation of a Genotyping Method for Analysis of TPMT Polymorphisms

BackgroundThiopurine methyltransferase (TPMT) catalyzes the methylation of thiopurine drugs such as azathioprine and 6-mercaptopurine. Several mutations in the TPMT gene correlate with low enzyme activity and adverse effects such as myelotoxicity. Hence, genotyping TPMT makes it possible to identify patients at high risk for drug toxicity.ObjectiveThe aim of this study was to validate a TPMT genotyping method by comparing it with a conventional polymerase chain reaction (PCR) approach.MethodsLightSNiP is a real-time PCR method for the detection of TPMT*2, *3B, and *3C without a sequencing step. We evaluated the frequencies of 3 TPMT alleles in 111 white adult patients by comparing genotyping by LightSNiP with conventional PCR (sequencing).ResultsNo differences were observed between conventional genotyping with sequencing and LightSNiP for *2, *3B, and *3C, suggesting the validity of this method.ConclusionsCompared with the conventional PCR sequencing method, the data suggest that LightSNiP correctly detected the TPMT *2, *3B, and *3C in this select population.