Near-normal urinary albumin concentrations predict progression to diabeticnephropathy in Type 1 diabetes mellitus

Aims To determine urinary albumin concentrations that predict progression t o diabetic nephropathy and sight-threatening diabetic retinopathy and ident ify baseline parameters associated with progression. Methods One thousand two hundred and one Type 1 diabetic patients aged 35 y ears or younger at diagnosis attending six hospital diabetes clinics in Sco tland and included on the Royal College of Physicians of Edinburgh Diabetes Register were followed for a median (interquartile range) of 4.0 (2.5-5.5) years. Diabetic nephropathy was defined as the geometric mean of two conse cutive urinary albumin values > 200 mg/l or a single value > 1000 mg/l. Ret inopathy was defined as clinician-determined maculopathy or proliferative r etinopathy. Results Forty-six patients developed nephropathy (4%) and 98 retinopathy (8 %). Cox proportional hazards analyses demonstrated that a baseline urinary albumin concentration above 7.4 mg/l, longer duration of diabetes and highe r HbA(1c) levels predicted the development of nephropathy. Higher baseline urinary albumin concentrations were the most powerful predictor for the dev elopment of nephropathy. Longer duration of diabetes, baseline blood pressu re > 140/90 mmHg and higher HbA(1c) levels all predicted the development of sight-threatening retinopathy whereas baseline urinary albumin concentrati on did not. Conclusions Elevation of urinary albumin concentration just above the norma l range is associated with an increased risk of developing diabetic nephrop athy. Identifying patients with any abnormalities of urinary albumin excret ion will provide a clear rationale for early therapeutic interventions.