Beta 2-glycoprotein-1 (apolipoprotein H) excretion and renal tubular malfunction in diabetic patients without clinical proteinuria.
OBJECTIVE
To compare the urinary excretion of beta 2-glycoprotein-1 with that of two other markers of early tubular disorder in diabetic patients without clinical proteinuria.


METHODS
The urinary excretion of retinol binding protein, beta 2-glycoprotein-1, and N-acetyl-beta-D-glucosaminidase was measured in 90 known diabetic patients who had a negative reagent strip test for proteinuria.


RESULTS
Among 43 patients with urinary albumin excretion within the reference range, 23 (53%) had raised urinary N-acetyl-beta-D-glucosaminidase activity, five (12%) increased excretion of beta 2-glycoprotein-1, and five (12%) increased loss of retinol binding protein. Among 47 patients with an albumin excretion of 0.9-7.9 mg/mmol creatinine, 42 (89%) had increased urinary N-acetyl-beta-D-glucosaminidase, 23 (49%) an increased output of beta 2-glycoprotein-1, and 16 (34%) a raised excretion of retinol binding protein. The excretion of these markers of tubular defects seldom exceeded two and a half times the upper reference limit and the differences between the findings in the insulin dependent and non-insulin dependent patients with similar albumin excretion were small and insignificant.


CONCLUSIONS
In diabetic patients with a negative dipstick test for proteinuria: (a) assay of urinary beta 2-glycoprotein-1 may be a more sensitive test for the detection of impaired tubular reabsorption of protein than measurement of retinol-binding protein; (b) assay of N-acetyl-beta-D-glucosaminidase can detect tubular injury at a time when protein reabsorption remains normal; and (c) impaired renal tubular function may be present in the absence of evidence of glomerular malfunction.
Lapsley
M
M
Department of Chemical Pathology, University College and Middlesex School of Medicine, London.
Flynn
F V
FV
Sansom
P A
PA
D000118:Acetylglucosaminidase / Q000652:urine; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001053:Apolipoproteins / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D003920:Diabetes Mellitus / Q000503:physiopathology / Q000652:urine*; D003922:Diabetes Mellitus, Type 1 / Q000652:urine; D003924:Diabetes Mellitus, Type 2 / Q000652:urine; D005260:Female; D006023:Glycoproteins / Q000652:urine*; D006801:Humans; D007684:Kidney Tubules / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012177:Retinol-Binding Proteins / Q000652:urine; D053482:beta 2-Glycoprotein I
D001053:Apolipoproteins; D015415:Biomarkers; D006023:Glycoproteins; D012177:Retinol-Binding Proteins; D053482:beta 2-Glycoprotein I; D000118:Acetylglucosaminidase