NAT2*74 is assigned unknown function based on a lack of evidence. NAT2*74 is defined by the core SNVs c.803G>A (p.R268K) and c.845A>G (p.K282R). c.803G>A (p.R268K) defines NAT2*4, formerly considered the reference allele, which has repeatedly shown increased function in vivo and in vitro. There is no literature describing function for c.845A>G (p.K282R). Three out of ten variant effect predictors tested by CPIC staff predict that c.845A>G (p.K282R) impairs protein function.