New research suggests that the higher rates of end-stage renal disease (ESRD) and progression of chronic kidney disease (CKD) seen in black patients compared with white patients are linked to renal risk variants in the gene encoding apolipoprotein 1 (APOL1).

The findings emerged from two large National Institutes of Health-funded study cohorts: the African American Study of Kidney Disease and Hypertension (AASK) and the Chronic Renal Insufficiency Cohort (CRIC).

Dominic S. Raj, MD, of George Washington University in Washington, DC, and fellow investigators acknowledged in their report for The New England Journal of Medicine (2013;369:2183-2196) that among U.S. patients with CKD, black patients are at higher risk for ESRD than white patients. The researchers examined the effects of variants in APOL1 in 693 black AASK participants with CKD attributed to hypertension, and in 2,955 black or white CRIC participants with CKD, 46% of whom had diabetes. Patients were evaluated according to whether they had two copies of high-risk APOL1 variants (APOL1 high-risk group) or zero or one copy (APOL1 low-risk group).

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The primary outcome in the AASK study was a composite of ESRD or a doubling of serum creatinine level. This outcome occurred in 58.1% of the APOL1 high-risk group and in 36.6% of the APOL1 low-risk group.

In the CRIC study, the primary outcomes were the slope in the estimated glomerular filtration rate (eGFR) and the composite of ESRD or a reduction of at least 50% in the eGFR from baseline. Black patients in the APOL1 high-risk group had a faster decline in eGFR and a higher risk of the composite renal outcome than did white patients, among those with diabetes and among those without diabetes.

“This study shows that APOL1 variant confers risk for progression of kidney diseases, independent of blood pressure control and diabetic status in African Americans,” Dr. Raj said in a statement from George Washington University.

Calling CKD “one of the most glaring examples of racial and ethnic disparities in health outcomes in the United States,” Dr. Raj stated that the research highlights the need for further studies that could lead to risk stratification and early and targeted interventions.