Comparison of the measurement of lipids and lipoproteins versus assay of apolipoprotein B for estimation of coronary heart disease risk: a study in familial combined hyperlipidemia.

We compared in 506 members of families with familial combined hyperlipidaemia (FCH), two approaches to selecting subjects with an apparent increased risk for coronary heart disease: assay of apolipoprotein (apo) B only versus measurement of plasma lipids and lipoproteins. When comparing both criteria, there was an overlap of 81.2% at apo B levels < or = 1250 mg/l and of 86.9% at apo B levels > 1250 mg/l. At apo B < or = 1250 mg/l all subjects were normolipidemic. However, 18.8% of these subjects had sub-normal HDL-cholesterol concentrations (< 0.9 mmol/l) but were not considered to have an increased risk because of very low LDL-cholesterol levels (< 2.5 mmol/l). At apo B concentrations > 1250 mg/l we observed a group with normal plasma lipid levels (13.1%). In this group, defined as normolipidemic hyperapobetalipoproteinemia, and considered to have an increased risk for coronary heart disease, apo B determination was thus most informative. The selection of the subgroup with 'normolipidemic hyperapobetalipoproteinemia' on the basis of the conventional approach could be refined using a cut off limit for plasma triglycerides < 1.5 mmol/l. This limit distinguished optimally between an atherogenic very dense LDL pattern versus a dense and buoyant pattern. Thus, based on the results of our study, the determination of apo B appeared to be, if not superior, at least as effective as the conventional lipid and lipoprotein parameters in classifying subjects at increased risk for coronary heart disease.