Abstract
Retinol-binding protein (RBP) is a low molecular weight protein freely filtered at the glomerulus. The fractional tubular reabsorption of RBP is 99.97% and increased excretion is therefore a sensitive marker of tubular dysfunction. We obtained early-morning urine specimens from 151 well children, from newborn to 16 years of age. RBP was measured using an enzyme-linked immunosorbent assay, albumin by a radioimmunoassay and creatinine by a modified Jaffé reaction. Protein excretion was assessed by calculating the protein: creatinine ratio for early-morning urine samples. We found a fall in both RBP and albumin excretion with increasing age, particularly in the 1st year of life, with a much wider variation in values from the infants studied. The mean excretion of RBP for children aged 0–6 months [51.4 (0.6–4,719) μg/mmol] was significantly higher (P<0.001) than the mean for children aged 6 months to 16-years [15.0 (3.8–60) μg/mmol]. It has been shown that measurement of tubular proteinuria using the RBP: creatinine ratio is useful in the assessment of children with renal disease and we propose a value two standard deviations above the geometric mean for the age of the patient as an upper limit of normal.
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Smith, G.C., Winterborn, M.H., Taylor, C.M. et al. Assessment of retinol-binding protein excretion in normal children. Pediatr Nephrol 8, 148–150 (1994). https://doi.org/10.1007/BF00865463
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DOI: https://doi.org/10.1007/BF00865463