The frequency of CYP2C19 loss-of-function variants in patients with non-cardioembolic ischemic stroke or transient ischemic attack in the Dutch population

Introduction: The CYP2C19 enzyme converts clopidogrel into an active metabolite. Carriers of CYP2C19 loss-of-function (LOF) variants with a history of ischemic stroke or transient ischemic attack (TIA) using clopidogrel may have a higher risk of recurrent stroke. To study the implications of genetic CYP2C19 heterogeneity in treatment of cerebral ischemia, knowledge about the prevalence of CYP2C19 LOF variants within the population is important. We investigated the frequency of CYP2C19 LOF variants in patients with non-cardioembolic ischemic stroke or TIA in the Dutch population. Methods: We performed a single-centre observational study with a cross-sectional design in a Dutch thrombectomy-capable stroke center. We included all patients presenting with non-cardioembolic ischemic stroke or TIA. We determined the frequency of CYP2C19 LOF variants in the full cohort. Additionally, we compared the frequency of CYP2C19 LOF variants in two subgroups: patients with first-ever non-cardioembolic ischemic stroke or TIA versus patients with recurrent ischemic stroke or TIA using clopidogrel because of a history of ischemic stroke or TIA. Results: We enrolled 410 patients between 1 January 2021 and 1 July 2021. 109 (26.6%) patients were carriers of CYP2C19 LOF variants. We found no difference in the frequency of CYP2C19 LOF variants between patients with first-ever ischemic stroke or TIA versus patients with recurrent ischemic stroke or TIA using clopidogrel (25.9% versus 31.9% respectively, p = 0.31). Discussion and conclusion: About a quarter of patients with non-cardioembolic ischemic stroke or TIA in the Dutch population carry a CYP2C19 LOF variant. This is lower than estimates found in studies with Asian populations, but similar to estimates found among Caucasian patients in other parts of the world.