AMP publishes recommendations for clinical CYP2C19 genotyping allele selection
BETHESDA, Md. — Feb. 27, 2018 — The Association for Molecular Pathology (AMP), the premier global molecular diagnostics professional society, today published consensus, evidence-based recommendations to aid clinical laboratory professionals when designing and validating clinical CYP2C19 assays, promote standardization of testing across different laboratories and complement existing clinical guidelines. The report, “Recommendations for Clinical CYP2C19 Genotyping Allele Selection: A Report of the Association for Molecular Pathology,” was released online ahead of publication in the Journal of Molecular Diagnostics.
The cytochrome P450 2C19 (CYP2C19) gene is one of the most frequently tested pharmacogenetics (PGx) genes because it is involved in the phase I metabolism of many commonly prescribed medications. However, currently available CYP2C19 tests can produce variable results due to factors such as the choice of tested alleles, targeted testing of populations with varying ethnic backgrounds, as well as the technical performance of the various platforms. The AMP PGx Working Group was established to help standardize this process by recommending variants for inclusion in clinical CYP2C19 genotyping panels.
“Considering the complex nature of clinical PGx testing and interpretation, and its impact on patient care, there is a clear, practical need for standardizing these transformative assays,” said Victoria M. Pratt, PhD, Associate Professor of Medical and Molecular Genetics at Indiana University School of Medicine and AMP PGx Working Group Chair. “The AMP PGx Working Group started with CYP2C19 genotyping panels due to the widespread adoption of these tests and our desire to help physicians, pharmacists, researchers, and other stakeholders better understand what these panels include and what the test results mean.”
This new report offers a two-tier categorization of CYP2C19 alleles as an aid for designing CYP2C19 genotyping assays. Using criteria such as allele function, population frequency and availability of reference materials, the AMP PGx Working Group recommended a minimum set of alleles and their defining variants that should be included in all clinical CYP2C19 PGx tests (Tier 1). The team also defined a Tier 2 list of optional CYP2C19 alleles that do not currently meet one or more of the criteria for inclusion in Tier 1. These recommendations are intended to facilitate testing by laboratories and improve genotyping concordance across laboratories.
“Pharmacogenetics is a rapidly changing field and molecular diagnostic laboratories must have updated resources and reference materials to guide them in their efforts to offer high-quality testing,” said Karen E. Weck, MD, Director of the Medical Genetics Laboratory at University of North Carolina School of Medicine and AMP PGx Working Group Member. “AMP members are among the early adopters of PGx testing in clinical settings and we are committed to publishing and updating a series of recommendations for informative PGx genes beyond CYP2C19, as part of our ongoing quest to continuously improve professional practice and patient care.”