Continuous-flow system for automation of latex immunoassay by particle counting

Latex immunoassay is a nonisotopic method based on agglutination, by protein, of calibrated latex particles coated with a specific antibody. The assay has been automated in a simple continuous-flow system by incubating the reaction mixture in a heated mixing coil for 25 min and measuring the agglutination with a cell counter. No external shaking of the latex suspension and no additional reagent is required for the agglutination. The method can accurately and precisely quantify a wide variety of proteins in plasma and urine, including human ferritin, beta 2-microglobulin, retinol-binding protein, and albumin. Depending on the antigen-antibody system, the detection limit ranges from 10(-10) to about 10(-12) mol/L. Within- and between-assay CVs are less than 10%. In the assay of ferritin, sera are pretreated to eliminate interferences from chylomicrons, complement, and rheumatoid factor.