Objectives: We have developed a competitive chemiluminescent immunoassay for the sensitive measurement of apolipoprotein B100 (apoB) and conducted a preliminary evaluation of the method.
Design and methods: In the assay, apoB-rabbit immunoglobulin G (IgG) conjugate competes with apoB in the sample for binding to acridinium N-hydroxysuccinimide labelled anti-apoB antibody. Goat anti-rabbit-IgG immobilized to magnetic particles is used to separate the apoB-rabbit IgG conjugate bound to the labelled anti-apoB antibody. Chemiluminescence, measured using a Ciba Corning Magic-Lite chemiluminometer, is inversely proportional to the concentration of apoB in the sample.
Results: The assay is completed in 1-2 h. Within-run imprecision (n = 5) determined at 10, 100, and 200 micrograms/L of apoB was found to be 4.8%, 2.4%, and 3.5%, respectively. The between-run imprecision (n = 5) at the same concentrations of apoB was determined to be 14.2%, 9.5%, and 7.7%, respectively. The proposed assay showed reasonable correlation (r = 0.86) with a commercially available immunoturbidimetric method. The lower limit of detection was 2.2 micrograms/L (4.0 pmol/L).
Conclusions: This assay may be useful in tissue culture studies where sensitive measurement of secreted and intracellular concentrations of apoB are required. Our preliminary evaluation of the assay appears to confirm is usefulness.