APOL1 and chronic kidney disease: In the African American Study of Kidney Disease and Hypertension comprising 693 black patients with hypertensive CKD, Parsa et al. [16] used a codominant genetic model to show that patients with the APOL1 two-risk allele had a 2-fold risk of doubling their serum creatinine from baseline or developing incident end-stage renal disease over a 9-year period of follow-up.