A HIGHLY accurate new assay method for the determination of low-density lipoprotein (LDL) cholesterol overcomes many of the shortcomings of existing techniques, says Randox. Its new direct clearance LDL assay promises excellent correlation with the ultracentrifugation method, which is accurate but difficult and costly to perform.
LDL cholesterol, commonly referred to as ‘bad’ cholesterol, is implicated in coronary artery disease when found at elevated levels in human blood. Determination of LDL cholesterol can be done by ultracentrifugation, which separates the various types of lipoproteins by their density. This is a very accurate laboratory technique, but because it is time consuming and difficult to automate it is not always made available.
An alternative technique is the calculation of LDL using the Friedewald equation. If triglyceride and high density lipoprotein (HDL) cholesterol levels are known, and are within certain parameters, this gives an inferred level of LDL. The restrictions on the technique, and the fact that it is unreliable in the presence of chylomicrons and beta-VLDL (very low density lipoprotein), are important considerations when contemplating this approach.
Randox says the trade-off of accuracy for convenience is no longer necessary, using its new two-step clearance method. All non-LDL components are first removed from the sample using the company’s reagents, before LDL is accurately measured in the second step. Randox claims a 99% correlation with the ultracentrifugation technique (ie, a correlation coefficient of 0.99) and the potential for straightforward laboratory automation of the procedures.
A further advantage is that all reagents are supplied in liquid form, eliminating reconstitution errors and reducing the chances of contamination. The company’s reagent range includes products covering the full range of lipids, including HDL, sLDL, and total cholesterol as well as lipoprotein (a), apolipoprotein A-1, A-II, B, C-II, C-III, and E, and triglycerides.