This study aims to characterize if differences in CYP2C19 genotype would lead to higher odds of long-term reoccurrence of ischemia stroke in stroke patients in an Asian cohort whereby pleomorphisms are more common. 

Clopidogrel is an anti-platelet utilised for secondary prevention of strokes. However, clopidogrel is a pro-drug activated in the liver, with current evidence showing variability in its anti-platelet effect due to differences in metabolism, notably by CYP2C19. 

This retrospective study included 268 consecutive patients with first-time ischaemic stroke. Data from subjects were collected from their outpatient visits and hospital database up to 31 October 2017 and retrospectively analysed after follow-up for seven years. A multivariate cox regression test was performed to assess overall risk of stroke recurrence for each genotype with correction for significant factors like age and hypertension. 

Only reoccurrence of stroke in the second and third year were significant, HR 0.335 (CI 0.123-0.911), HR 0.396 (CI 0.162-0.968) respectively with p<0.05. For reoccurrence of strokes beyond the 4th year or the cumulative reoccurrence of strokes, clopidogrel resistance was statistically insignificant (p>0.05).

Loss of function allele of CY2C19 was associated with increased reoccurrence of stroke in the second and third year due to reduced anti-platelet effect. Therefore, it is advisable to genotype these patients. However, CY2C19 genotype was not associated with increased risk of reoccurrence of stroke in the long-term. This was likely to occur due to other compensatory mechanisms and more important co-morbidities like hypertension, reducing the need to genotype such patients.