Electroimmuno-and ImmunonephelometricAssays of ApolipoproteinA-I by Using a Mixture of Monoclonal Antibodies

The use of mixtures of well-defined monoclonal antibodies may represent a step forward in the standardization of immunochemical assays. We developed and optimized working conditions for using such a mixture to determine apolipoprotein A-I in human sera by two independent tech-niques (electroimmuno- and immunonephelometric-assays). Six monoclonal antibodies, each addressed to distinct epi-topes located at the surface of apolipoprotein A-I, were used in combination to permit a reproducible measurement of the protein, without prior delipidation of samples. Parallel stan-dard curves for a high-density lipoprotein subfraction (HDL3, the primary standard) and a reference serum (the secondary standard) were obtained. Within- and between-run coeff i-cients of variation were acceptable for both methods. Apo-lipoprotein A-I concentrations, as measured in 60 subject