What does the Cytochrome P450 2C19 Genotype test measure?

Why is Cytochrome P450 2C19 Genotype measured?

Carriers of CYP2C19 loss-of-function alleles produce less active metabolite, exhibit diminished platelet inhibition, and face higher rates of major adverse cardiovascular events — particularly stent thrombosis — after percutaneous coronary intervention. Guidelines from multiple cardiology and pharmacogenomics consortia recommend alternative P2Y12 inhibitors (prasugrel or ticagrelor) for intermediate and poor metabolisers undergoing PCI. Conversely, ultrarapid and rapid metabolisers may have increased bleeding risk, though the evidence is less robust. Genotype-guided antiplatelet therapy is an established application of pharmacogenomics in cardiovascular medicine.

Reference ranges

Standard reference

Reported as genotype (e.g. *1/*1, *1/*2, *2/*17) and phenotype classification: ultrarapid, rapid, normal, intermediate, or poor metaboliser.

Functional medicine optimal

Not applicable; results are genotypes (diplotypes) translated into a metaboliser phenotype. 'Optimal' in the clinical sense is a normal or rapid metaboliser phenotype when clopidogrel is prescribed, prompting alternative therapy for intermediate and poor metabolisers.

Units

Genotype classification, Genotype

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.