Automated immunoturbidimetric methods for the determination of retinol binding protein, prealbumin and transferrin in urine

We describe the development of rapid and simple automated methods for the estimation of retinol binding protein (RBP), prealbumin (PA) and transferrin (TRF) in urine. These methods measure the turbidity formed as a result of reaction between the protein and a specific antibody in a phosphate buffer containing 70 g/L polyethyleneglycol as accelerator for the antigen antibody reaction. The method for retinol binding protein (RBP) correlated well when compared with a method based on enzyme-linked immunosorbent assay (ELISA) (r = 0.978). The recoveries were 93-104%, 84-95% and 84-100% for RBP, PA and TRF respectively. The between-batch coefficients of variation were 2.6-10.6, 2.8-12.6 and 4.2-8.7% respectively. The analytical range of the method was 0.0625 to 40 mg/L for RBP, 0.28 to 45 mg/L for PA and 0.14 to 70 mg/L for TRF. The methods can be performed manually using a simple spectrophotometer or can be easily automated.