Abstract
Serum creatinine-based estimated glomerular filtration rate is widely used to assess kidney function but is influenced by nonrenal determinants of creatinine production. The recent identification of an African ancestry-specific glycine amidinotransferase variant that increases creatine synthesis and serum creatinine without affecting measured kidney function provides a biological explanation for part of the residual bias in creatinine-based estimated glomerular filtration rate among individuals of African ancestry.