Measurement of urinary retinol-binding protein by enzyme-linked immunosorbent assay, and its application to detection of tubular proteinuria.
An enzyme-linked immunosorbent assay (ELISA) for urinary retinol-binding protein (RBP) has been developed and compared with urinary beta 2-microglobulin for the detection of tubular proteinuria. The assay has a working range of 10 to 250 micrograms of RBP per liter of urine. The within-assay CV was 3.2-7.1%, the between-assay CV 12.5%. A control population of 118 male subjects gave a geometric mean urinary RBP concentration of 7.7 micrograms per millimole of creatinine and a 95th centile of 22 micrograms per millimole of creatinine. Comparison of urinary RBP and beta 2-microglobulin concentrations in 80 control subjects and 117 subjects exposed to cadmium fumes gave correlations of r = 0.59 and 0.91, respectively. Of the 117 subjects exposed to cadmium fumes, 103 gave both RBP and beta 2-microglobulin concentrations on the same side of the upper 95th centile values of 22 and 38 micrograms per millimole of creatinine for RBP and beta 2-microglobulin respectively (Chi-square analysis p less than 0.001), demonstrating that RBP and beta 2-microglobulin detect tubular proteinuria with equal sensitivity and specificity. ELISA and an established latex immunoassay gave well-correlated results.
D000328:Adult; D000368:Aged; D002104:Cadmium / Q000009:adverse effects; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007118:Immunoassay; D007674:Kidney Diseases / Q000139:chemically induced / Q000503:physiopathology; D007684:Kidney Tubules / Q000503:physiopathology*; D007840:Latex; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000139:chemically induced / Q000503:physiopathology; D011507:Proteinuria / Q000652:urine*; D012177:Retinol-Binding Proteins / Q000652:urine*; D001613:beta 2-Microglobulin / Q000652:urine
D007840:Latex; D012177:Retinol-Binding Proteins; D001613:beta 2-Microglobulin; D002104:Cadmium