We compared the urinary excretion of albumin, transferrin, N-acetyl-β-D-glucosaminidase and α-1-microglobulin in 78 Type 1 (insulin-dependent) diabetic patients: 39 with retinopathy and 39 without. The two groups were matched for age, sex and duration of diabetes. The patients with retinopathy had increased excretion (median and range) of albumin [1·7 (0·3–399·1) versus 1·0 (0·3–116·6) mg/mmol creatinine, P < 0·05], transferrin [114·2 (4·1–37126·2) versus 33·4 (1·0–4176·7) μg/mmol creatinine, P < 0·01] and N-acetyl-β-D-glucosaminidase [23·8 (1·1–119·1) versus 15·0 (0·1–65·1) μmol/h/mmol creatinine, P < 0·05] but not α-1-microglobulin. Transferrin excretion correlated with albumin excretion. The prevalence of increased transferrin excretion (transferrinuria) was greater than that of microalbuminuria in patients both with and without retinopathy (P < 0·01 in both cases). Urinary transferrin seems likely to be predominantly of glomerular origin and merits prospective longitudinal evaluation as a potential index of the microangiopathic process.
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