Solid-phase fluoroimmunoassay of human albumin in biological fluids

A simple fluoroimmunoassay for the determination of albumin levels in serum, urine and cerebrospinal fluid is described. It employs magnetisable particles to which antibodies to human serum albumin are covalently linked, and albumin labelled with fluorescein. Equilibrium is reached within 30 min, when separation of the bound and free fractions of the labelled albumin is performed by precipitation of the particles either with a magnet or by centrifugation. Measurement of the fluorescence in the supernatant (the free fraction) reflects the albumin concentration of the standards or samples. Correlation studies with an automated immunoprecipitation technique show good agreement.