CYP2C19*28 is assigned normal function based on limited in vitro and computational evidence. An in vitro study found CYP2C19*28 had similar intrinsic clearance compared to wildtype with a mephenytoin substrate (25001882). A computational analysis including splice site, mFold and nonsynonymous mutation analysis, did not find a deleterious impact on enzyme function (20712527). Although CYP2C19*28 was found to have increased intrinsic clearance compared to wildtype with a clopidogrel substrate in vitro (25001882), the experts did not find this result convincing as computational analysis and in vitro data with mephenytoin did not support increased function. Therefore, consensus among experts was normal function based on limited evidence as it was determined the phenotypes containing this allele would be clinically similar to phenotypes comprising normal function alleles.