NAT2*53 is assigned decreased function based on moderate evidence. NAT2*53 is characterized by the core SNVs c.248G>C (p.G83A), c.590G>A (p.R197Q) and c.803G>A (p.R268K). 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 experimental evidence describing function for c.248G>C (p.G83A). Seven out of nine variant effect predictors tested by CPIC staff predict that c.248G>C (p.G83A) impairs protein function. Similarly, published in silico analysis indicates that c.248G>C (p.G83A) is deleterious for protein function (Abodlaa et al. 2019; Bilal et al. 2022). c.590G>A (p.R197Q) defines NAT2*6 which has been extensively studied, exhibiting decreased N-acetyltransferase activity both in vivo and in vitro. Similarly, seven out of nine variant effect predictors tested by CPIC staff predict that c.590G>A (p.R197Q) impairs protein function. Thus, NAT2*53 is assigned decreased function based on c.590G>A. Despite this, the combinatorial effects associated with c.248G>C and c.590G>A are uncertain.