A Novel Laboratory-Developed Test Using Multiplex qPCR to Further Personalize Tacrolimus Dosing

Tacrolimus is an immunosuppressant drug commonly used in transplantation. Although multiple studies have demonstrated that polymorphisms in the CYP3A5 gene impact the metabolism of tacrolimus, routine pre-transplant testing for these markers is still not broadly implemented. TacroType™—a new laboratory-developed test implemented by One Lambda Laboratories—utilizes a qPCR-based six-plex assay for CYP3A5 genotyping and detects the three most common genetic variants (*3, *6 and *7) associated with loss of CYP3A5 protein function and reduced tacrolimus metabolism. TacroType was optimized to address known sources of protocol, technical or sample variability to achieve accurate and reproducible genotyping results. An analytical performance study was completed following CLSI guidelines. Accuracy was confirmed for each possible CYP3A5 genotype involving six target alleles using 32 well-characterized reference samples. TacroType exhibited accurate performance within a broad range of DNA concentrations and quality. Precision studies indicated consistent genotyping results across four operators, two instrument types and five lots of reagents. Accurate and reproducible assay performance was demonstrated using whole blood from 95 donors and buccal swabs from 65 donors. The analytical performance of TacroType was evaluated in 4014 total qPCR reactions, with a report rate of 99.8% and genotyping accuracy of 100% (95% confidence interval of 99.9%).