Competitive enzyme immunoassay for apolipoprotein A-II.

A competitive enzyme immunoassay for apolipoprotein A-II was developed. Microtitre plates were used as a solid phase and coated with anti-apolipoprotein A-II antibodies. Purified apolipoprotein A-II, labelled with horseradish peroxidase was used as competing ligand. The assay was examined with respect to the optimal amounts of specific anti-apolipoprotein A-II antibodies and apolipoprotein A-II-enzyme conjugate. The displacement curves showed a good parallelism between serum and purified apolipoprotein A-II. Delipidation of serum did not affect the content of apolipoprotein A-II. Cross-reactivity with apolipoprotein A-I was minimal. The intra- and inter-assay coefficients of variation in the medium range were 9.0 and 11.8% respectively. The assay might be well-suited for clinical routine.