Hyperfiltration in Normoalbuminuric Type 1 Diabetic Patients: Relationship with Urinary Albumin Excretion Rate

Hyperfiltration has been documented in type 1 diabetes and may contribute to the high risk for development of albuminuria and progression of nephropathy. However, recent studies suggest that the risk of progression to albuminuria in type 1 diabetes was not increased by hyperfiltration. We investigated associations of estimated glomerular filtration rate (eGFR) and urinary albumin excretion rate (UAE) in normoalbuminuric type 1 diabetic patients. Study included 313 normoalbuminuric patients with type 1 diabetes, none showed signs of adrenal, renal, or cardiovascular diseases. GFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. Glomerular hyperfiltration was defined as eGFR >= 125 mL min(-1) 1.73 m(-2). Renal hyperfiltration was present in 12% of the study group. Subjects with eGFR >= 125 mL min(-1) 1.73 m(-2) were younger, had shorter duration of diabetes, lower levels of total and LDL cholesterol, and higher HbA1c than subjects with an eGFR below 125 mL min(-1) 1.73 m(-2). Type 1 diabetic patients with hyperfiltration also had significantly lower UAE. In a multiple logistic regression analysis, higher eGFR was associated with lower UAE. Our results indicate that normoalbuminuric type 1 diabetic patients with hyperfiltration have lower UAE than those with renal function in the normal range. Together with other recent studies this may suggest that creatinine-based estimates of GFR indicating hyperfiltration is not associated with higher UAE and subsequent development of microalbuminuria.