Immunoturbidimetric measurement of serum retinol-binding protein in renal and hepatic disease.

Serum retinol-binding protein (RBP), with a biological half-life of less than 12 h, is a useful indicator of liver or kidney dysfunction. An automated immunoturbidimetric assay for the measurement of RBP has been developed using the Cobas-BIO centrifugal analyser and commercially available materials. Serum samples with RBP concentrations as low as 3 mg/L were measured. Within-run and day-to-day imprecision were 3.7 and 5.7%, respectively. The reference range (mean +/- 2SD) for 51 adults was 17 to 61 mg/L. Slight haemolysis of serum (haemoglobin 10 g/L) resulted in an apparent 8% reduction of RBP with greater interference at higher haemoglobin concentrations. However, bilirubin in concentrations up to 0.15 g/L did not interfere with RBP measurements. There was good correlation between immunoturbidimetry and a commercial radial immunodiffusion method. Serum RBP concentrations were decreased in liver disease and increased in renal failure.