NAT2*48 is assigned decreased function based on limited evidence. The NAT gene nomenclature committee has historically assigned acetylation activity to alleles as either "rapid" or "slow", classifying the NAT2*48 allele as "slow" . Under the CPIC allele function terminology, slow acetylation alleles are categorized as "Decreased Function". In vitro evidence demonstrates that NAT2*48 N-acetylation activity is undetectable when using sulfamethazine as a substrate. NAT2*48 mRNA expression levels are comparable to NAT2*4, but protein expression is undetectable in mammalian cells (17264801, 17434923). Despite the undetectable enzymatic activity, the authors concluded that NAT2*48 exhibits decreased function rather than no function. Similarly, the committee could not come to consensus on a call of no function due to the lack of in vivo data supporting a complete loss of function. Published in silico modeling suggests that c.364G>A (p.D122N) disrupts the catalytic triad and the stability of the active site loop (18680467). Eight out of ten variant effect predictors tested by CPIC staff predict that c.364G>A (p.D122N) impairs protein function.