The CYP2C19*3 allele is assigned as a no function allele by CPIC. Patients carrying the CYP2C19*3 allele in combination with a no, decreased, normal, or increased function allele who are treated with clopidogrel may have decreased platelet inhibition and increased residual platelet aggregation as compared to patients with two normal function alleles. However, conflicting evidence has been reported. Other genetic and clinical factors may also influence platelet inhibition.