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 μL 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 μg/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.
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