Turbidimetric latex immunoassay for serum ferritin

A sensitive immunoassay based on latex particle agglutination (latex immunoassay) has been developed for the determination of serum ferritin. Polystyrene particles (0.8 micron) to which anti-ferritin antibody is adsorbed are incubated with serum for 30 min with shaking or 60 min without shaking. The resulting agglutination is quantified by measuring the decrease of absorbance of the latex suspension at 360 nm. Pretreatment of the serum is required to prevent interference from complement, rheumatoid factor and chylomicrons. The lowest detectable concentration of ferritin in serum is about 5 micrograms/l. Within-runs and between-runs coefficients of variation, based on analysis of samples containing 14-820 micrograms/l ferritin, ranged from 3.6 to 13.8%. A correlation coefficient of 0.95 between latex immunoassay and radioimmunoassay was obtained for the determination of ferritin in 46 sera.