Diabetic Nephropathy Progression Not Driven by Ethnicity
Hugh C. Rayner, MD
ISTANBUL –Contrary to a widely held view, South-Asian and white European diabetic patients with moderately reduced kidney function have essentially the same rate of nephropathy progression, according to study findings reported at the 50th Congress of the European Renal Association-European Dialysis and Transplant Association.
“The standard wisdom based on several earlier reports is that nephropathy progresses at a faster rate in South-Asian diabetic patients than in their white European counterparts,” said Hugh C. Rayner MD, consultant nephrologist at Heart of England National Health Service (NHS) Foundation Trust in Birmingham, U.K.
The data showed that despite having worse glycemic control, South-Asian patients with diabetes and chronic kidney disease stage 3 did not differ from white European patients in the rate of decline in estimated glomerular filtration rate (eGFR) over a five-year follow-up period.
“We are trying to reduce inequalities in health between different parts of our population, and we wanted to make sure that kidney treatment was not worse for South-Asian patients than for white European patients,” Dr. Rayner commented. “From our data, it seems that we can achieve the same outcomes for the two ethnic groups, and we find that reassuring.”
The study included patients with diabetes who had attended a diabetes or renal outpatient clinic with eGFR values of 30 mL/min/1.73 m2 or higher but less than 60 mL/min/1.73m2 from January 2001 through December 2005.
About three quarters of the 1,012 study participants were white European, and the remaining subjects were South-Asian (from the Indian subcontinent).
The researchers observed no difference in baseline eGFR between South-Asian and white European patients (median of 49.7 and 51.7 mL/min/1.73m2, respectively).
South-Asian patients were younger than white European patients (68 vs. 70 years) and had worse baseline glycemic control as indicated by lower hemoglobin (Hb) A1C level (8.0% vs. 7.6%).
After five years, eGFR was a mean of 46.8 mL/min/1.73m2 in South-Asian patients and 45.9 mL/min/1.73m2 in white European patients. In addition, the mean change in eGFR over the study period was -2.9 and -3.2 mL/min/1.73m2 for the two groups, respectively.
Overall, 35 (12.4%) patients in the South-Asian group and 82 (9.2%) patients in the white European group progressed to stage 4 or 5 CKD. The data showed a trend towards higher five-year follow-up HbA1c levels in South-Asian than in white European patients.
Dr. Rayner said that the findings bolster prior research showing that glycemic control is not the main determinant of the rate of progression of kidney disease in diabetic patients with moderate reduced renal function. The main reversible factor that influences the progression of diabetic nephropathy is blood pressure (BP), but the link between BP control and progression was not examined in this study.
“The message is that there is no intrinsic genetic predisposition for South-Asian with diabetes and kidney disease to worsen more quickly,” Dr. Rayner said. “We worry that doctors may believe that deterioration is inevitable. We believe that if you keep doing everything correctly, you can achieve equal outcomes in South-Asian and white European patients.”