SENSITIVE ASSAYS FOR URINARY RETINOL-BINDING PROTEIN AND BETA-2-GLYCOPROTEIN-1 BASED ON COMMERCIALLY AVAILABLE STANDARDS

Measurements of urinary retinol-binding protein (RBP) and beta-2-glyco protein-1 (beta 2G1) provide sensitive indicators of proximal renal tu bular malfunction. beta 2G1 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 on e urine dilution. The assays both use widely available commercial stan dards and permit accurate measurement throughout most of the reference range. We measured both proteins in the urine of 70 healthy adults an d 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 mu g/mmol RBP (median 8) and up to 30 mu g/mmol beta 2G1 (median 15) with no differe nce between the sexes. Children had different ranges to adults with ex cretion of up to 22 mu g/mmol RBP (median 10) and up to 80 mu g/mmol b eta 2G1 (median 24).