Measurement of serum low density lipoprotein-cholesterol in patients with hypertriglycemia

Low density lipoprotein-cholesterol (LDL-c) concentration measured by a hom ogeneous enzymatic assay was reported to correlate well with the modified b eta-quantification assay, especially in samples with high triglyceride (TG) concentration. In this study, we evaluated a homogeneous enzymatic assay, Cholestest(R)-LDL assay system, in hypertriglycemic patient samples, and fo und that 56% (9/16) of serum samples with intermediate TG concentrations (2 .27-4.52 mmol/L) showed more than 10% discrepancy with concentration by the modified beta-quantification assay. Such serum samples originated from pat ients with hyperglycemia of type II a (three cases), type II b (two cases), type III (one case), and type IV (six cases). Differential staining of cho lesterol and triglyceride after agarose gel electrophoresis revealed that t hese serum samples contained significant amounts of intermediate fractions between pre-beta- and beta-lipoproteins. Since lipoprotein (a), which migra tes between pre-beta- and beta-lipoproteins, is not correlated with the dis crepancy, we believe the intermediate fraction consists of intermediate den sity lipoprotein (IDL) and a chylomicron remnant. A part of IDL and chylomi cron remnant, which contain a significant amount of triglyceride, might be measured as LDL-c by the homogeneous enzymatic assay, but not by the modifi ed beta-quantification assay.