Homogeneous Assay Measures Small Dense LDL Cholesterol

A rapid assay suitable for autoanalyzers has been devised to measure the concentration of SD-LDL cholesterol in blood samples and is much easier to use than the complex methods that require special equipment and long assay times.

Scientists at the Showa University School of Medicine, (Tokyo, Japan), have identified suitable surfactants and phospholipases by screening for those selective for the SD-LDL fraction (density range: 1.044 kg/L - 1.063 kg/L) and for the dissociation of other lipoproteins, including large buoyant LDL (lb-LDL). They compared this technique with ultracentrifugal isolation of LDL subfractions and with heparin-magnesium precipitation assay for SD-LDL. They measured SD-LDL-C concentrations in 460 healthy, normolipidemic individuals. Small, dense LDL is a type of LDL cholesterol that is considered to be an emerging risk factor for cardiovascular disease. It is smaller and heavier than typical LDL cholesterol and can increase the risk of developing atherosclerosis.

The homogeneous method correlated excellently with ultracentrifugation for SD-LDL-C and exhibited within-run precision. The distribution of SD-LDL-C was skewed, and the central 95% of SD-LDL-C concentrations ranged from 0.24 to 0.88 mmol/L (9.4–34.0 mg/dL). The homogeneous assay SD-LDL-C results for 60 samples from healthy volunteers were compared with those obtained by ultracentrifugation. Serum samples were obtained from these individuals who had variable serum lipid levels; LDL-C range: 1.6–5.2 mmol/L (63–199 mg/dL); triglycerides range: 0.3–5.2 mmol/L (30–472 mg/dL), and high-density lipoprotein cholesterol: 0.9–2.5 mmol/L (35–97 mg/dL).

The authors concluded that the homogeneous assay allows reproducible measurement of SD-LDL-C within 10 minutes and appears promising in further investigations of the clinical significance of SD-LDL-C. The study was published in December 2010, in Clinical Chemistry.

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