Although increased urinary albumin excretion may increase the risk of adverse renal outcomes in patients with diabetes, it remains unclear whether microalbuminuria is associated with a higher incidence of macroalbuminuria in the absence of non-diabetic kidney events that frequently develop during the long-term course of type 2 diabetes. This historical cohort study included patients with type 2 diabetes, spot urine albumin:creatinine ratio (ACR) <300 mg/gCr and normal serum creatinine concentrations treated between August 1988 and April 2015. Patients with any evidence suggesting non-diabetic kidney diseases at baseline were excluded. Over a median follow-up of 50 months, 70 of the 1760 included patients developed macroalbuminuria. Twenty-one of these patients were diagnosed with non-diabetic renal events. The five-year cumulative incidence of macroalbuminuria in patients with ACRs of 0–7.5 mg/gCr, 7.5–30 mg/gCr, 30–150 mg/gCr, and 150–300 mg/gCr were 0%, 0.53%, 3.5%, and 36.0%, respectively, with significant differences between each pair of ACR categories. In type 2 diabetes, higher urinary ACR, even within a level of normoalbuminuria, was associated with a greater incidence of macroalbuminuria when non-diabetic renal events were excluded. These results conflict with findings suggesting that microalbuminuria is a poor indicator for the progression of diabetic nephropathy.

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