Development of a rapid latex enhanced turbidimetric assay for retinol binding protein in urine

We describe a simple, rapid and sensitive homogeneous immunoassay for urinary retinol-binding protein (RBP) using latex particle-enhanced turbidimetric immunoassay. Rabbit anti-human RBP is covalently coupled to 40 nm latex particles and the assay performed on the IL Monarch 2000 centrifugal analyser, with a 20 microL sample volume and the reaction monitored at 340 nm over an 8 min period. The assay range is 0-6 mg/L with a detection limit of 25 micrograms/L. The within and between assay coefficients of variation are less than 1.5% and less than 2.5%, respectively. Comparison with radioimmunoassay for RBP showed good agreement.