Evaluation of a quantitative photometric latex agglutination immunoassay for alpha-foetoprotein

A simple quantitative photometric method is described for the determination of serum alpha-foetoprotein using latex particle agglutination in an immunochemical system. This method is based on the quantitative photometric measurement of agglutination of latex particles coated with antibodies against alpha-foetoprotein. The turbidity is measured at a wavelength of 340 nm. Agglutination causes a decrease in absorbance. Interference by serum constituents, e.g. rheumatoid factors, are avoided by pretreating the serum samples with buffered polyethylene glycol. Concentrations of 0 to 640 micrograms/l were used for the standard curve. Analytical recoveries were 99.5 to 105.2%. Maximum within and between runs coefficients of variation were 6.2 and 11.6%. The correlation coefficient of the method with radioimmunoassay (RIA), calculated from results on 117 serum samples, was 0.997, and the regression equation y = 0.99x (RIA) - 7.23.