Diabetic Retinopathy, Microalbuminuria Predict GFR Decline

Having diabetic retinopathy and/or microalbuminuria predicted a much higher rate of annual decline in glomerular filtration rate (GFR) in a new study of patients with type 2 diabetes living in Japan.

"The presence of microalbuminuria and/or [diabetic retinopathy] profoundly affects renal function in type 2 diabetic patients," according to Tatsumi Moriya, MD, from Kitasato University, Kanagawa, Japan, and colleagues. "Therefore, diabetologists and ophthalmologists should share their acquired information regarding [diabetic nephropathy] and [diabetic retinopathy], even if it is at milder stages," they conclude.

The study, based on data from the Japan Diabetes Complications Study (JDCS), a nationwide randomized controlled study of type 2 diabetic patients focusing on lifestyle modification, was published online April 25 in Diabetes Care.

Diabetic retinopathy is a known risk factor for microalbuminuria, and microalbuminuria is a risk factor for macroalbuminuria, but to date it has been unclear whether diabetic retinopathy predicts poor renal function, the authors write.

To examine this relationship, they analyzed data from 1475 patients in the JDSC, divided into 4 groups:

Normal urine albumin, no diabetic retinopathy (n = 773).
Normal urine albumin, with diabetic retinopathy (n = 279).
Microalbuminuria, no diabetic retinopathy (n = 277).
Microalbuminuria, with diabetic retinopathy (n = 146).

After a median follow-up of 8 years, compared with the patients with neither microalbuminuria nor diabetic retinopathy at baseline, those who had at least 1 risk factor were much more likely to progress to macroalbuminuria, especially if they had microalbuminuria.

Hazard Ratio for Developing Macroalbuminuria During 8 Years of Follow-up

Baseline Characteristics	HR (95% CI)	P
Normal Urine Albumin, No Diabetic Retinopathy	1 (reference)	—
Normal Urine Albumin, With Diabetic Retinopathy	2.48 (0.94 – 6.50)	0.07
Microalbuminuria, No Diabetic Retinopathy	10.40 (4.91 – 22.03)	<0.01
Microalbuminuria, With Diabetic Retinopathy	11.55 (5.24 – 25.45)	<0.01
CI = Confidence interval

The annual decline in the estimated glomerular filtration rate (eGFR) was 2 to 3 times faster in the group with both risk factors than in the other groups.

"It is absolutely necessary to stop the progression of [diabetic nephropathy] and to find biomarkers or easily available factors that represent the exact clinical course or prognosis of [renal-function decline]," say Moriya and colleagues. Microalbuminuria and diabetic retinopathy appear to be 2 such markers, and this type of patient information needs to be shared among specialists who are treating the same patients, they stress.

The authors have reported no relevant financial relationships.

Diabetes Care . Published online April 25, 2013. Abstract