Enzyme-Linked Immunosorbent Assay for Apolipoprotein B on Dried Blood Spot Derived from Newborn Infant

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Abstract
Hypercholesterolemia is a risk factor for atherosclerotic cardiovascular disease, and early diagnosis and treatment should be given attention. We developed a simple and sensitive enzyme-linked immunosorbent assay (ELISA) for apolipoprotein B (apoB) on a dried blood spot (DBS). The specificity of this assay was investigated by constructing curves for other proteins. The crossreactivity was negligible. The mean intra- and intercoefficients of variation were 5.2 and 7.8%, respectively. We used phosphate buffer with Triton X-100 for extracting apoB on DBS. The elution of apoB was stable up to 30 days after bleeding. The correlation between plasma and DBS apoB was r = 0.94, p < 0.005, n = 55. Using this method, we screened 2,500 babies between 5 and 7 days of age. The mean ± SD of DBS apoB was 75 ± 15 U. Seven hypercholesterolemic neonates were detected. Family studies of these neonates disclosed one definite and two suspected heterozygotes for familial hypercholesterolemia. Four other neonates showed no related familial background. This ELISA method for assaying apoB should prove to be a useful tool for large mass screening for hypercholesterolemia, particularly in the newborn.