Some Considerations of Methodology and Standardization of Apolipoprotein B Immunoassays

Apolipoprotein B, the major protein component of very-low-density (VLDL) and low-density (LDL) lipoproteins in serum, is being widely measured in serum, to help assess risk of cardiovascular disease. Standardization has proven difficult because of the physical and immunochemical heterogeneity of LDL and VLDL, the masking of antigenic determinants of LDL and VLDL, the insolubility of apolipoprotein B, the instability of lipoprotein reference materials, and the multiplicity of analytical methods. Here we have examined the literature and collected current information from lipoprotein scientists to determine the problems--and the ways investigators have attempted to solve them--in preparation, storage, and use of standards and anti-apolipoprotein B sera, analytical procedures and reagents, and the nature of apolipoprotein B in serum. Standardization appears possible with development of stable reference materials that are applicable to the various analytical methods, controlled immunochemical reaction conditions, and establishment of a selected interim reference method for use as a point of reference.