Abstract
Measurements of urinary retinol-binding protein (RBP) and β-2-glycoprotein-1 (β2G1) provide sensitive indicators of proximal renal tubular malfunction. β2G1 is very stable in urine but RBP, which is much less stable, has been more extensively studied. We have designed two similar immunoassays allowing measurement of both proteins from one urine dilution. The assays both use widely available commercial standards and permit accurate measurement throughout most of the reference range. We measured both proteins in the urine of 70 healthy adults and 80 healthy children aged between three and 16 years, expressing the results as a ratio to creatinine concentration. Using the 98th centile as the upper reference limit, adults excreted up to 17 μg/mmol RBP (median 8) and up to 30 μg/mmol β2G1 (median 15) with no difference between the sexes. Children had different ranges to adults with excretion of up to 22 μg/mmol RBP (median 10) and up to 80 μg/mmol β2G1 (median 24).