Pathology guideline standardizes warfarin genotype testing

2020 05 06 19 00 3862 Pharmacogenetics Theme 400

A new guideline from pathology societies provides a steer on what should be included in clinical warfarin sensitivity genotyping panels, as part of a larger move to standardize pharmacogenomics (PGx) testing in clinical laboratories.

The guideline was developed by the Association for Molecular Pathology (AMP) and the College of American Pathologists (CAP), with input from the Clinical Pharmacogenetics Implementation Consortium (CPIC). Recommendations were published by Dr. Karen Weck, director of the molecular genetics laboratory at the University of North Carolina, and colleagues online May 4 in the Journal of Molecular Diagnostics.

Testing is conducted routinely to identify patients who cannot metabolize the blood thinner warfarin, among other medications. The evidence-based recommendations build on past successes and improve phenotype prediction and test interpretation for all future warfarin sensitivity genotyping panels, according to the AMP.

The May 4 report is part of a series providing guidance on testing and aimed at standardizing PGx tests, and it builds on earlier recommendations for CYP2C19 and CYP2C9 genotyping, the AMP noted in a statement.

"Clinical PGx testing assays can vary significantly between laboratories," Weck and colleagues wrote in J Mol Diagn. "Some assays test for a single pharmacogene, while others test for several thousand variants in a variety of pharmacogenes."

These differences can result in discrepant genotyping results and discordant interlaboratory quality assessments in PGx proficiency testing surveys, and they may ultimately affect patient care, the authors wrote.

As with prior reports in the series, the document on warfarin sets out a minimum panel of variant alleles that should be included and an extended panel that may be considered by labs in designing PGx tests.

"Our ultimate goal is to promote standardization of PGx gene/allele testing across clinical laboratories," Weck and colleagues wrote. "These recommendations are not to be interpreted as prescriptive but to provide a reference guide."

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