Measurement of nine human milk proteins by nephelometric immunoassays: Application to the determination of mature milk protein profile

Objectives: Microparticle-enhanced nephelometric immunoassays for six human milk proteins (beta-casein, kappa-casein, alpha-lactalbumin, serum albumin , lactoferrin, and lysozyme) and conventional immunonephelometry assays for immunoglobulin A, C3, and C4 complement proteins were developed and charac terized. Design and methods: Microparticle-enhanced nephelometric immunoassays are c ompetitive assays based on the nephelometric quantification of the inhibiti on of microparticle-protein conjugates immunoagglutination by the proteins to be assayed. Results: High precision (CVs ranged from 1% to 14% in within- and between-a ssays) and recovery (linear recovery in dilution-overloading assay) ensure a reliable determination of the main human milk proteins by single-step hom ogeneous nephelometric immunoassays, accurate over wide ranges of concentra tion. These immunoassays were easily applied to a large number of mature hu man milk samples (between 373 and 503 according to the proteins tested). Conclusions: The immunoassays developed could be applied to the fast determ ination of human milk protein profile usable for nursery milk bank and fort ification. Copyright (C) 2000 The Canadian Society of Clinical Chemists.