Estimation of plasma very low density lipoprotein-cholesterol levels in uremia

Background. In investigations of plasma lipids and lipoproteins, very low density lipoprotein (VLDL)-cholesterol is often calculated from the level of plasma triacylglycerols (in mmol/l) divided by 2.2. This is then used to calculate low density lipoprotein (LDL)-cholesterol. This approach to quantifying lipoprotein levels is invalid for hypertriglyceridemic subjects and patients with type III or remnant hyperlipoproteinemia. It may also not give accurate results for subjects with other forms of dyslipoproteinemia, including patients with uremia or chronic renal failure. In the present study, a simple ultracentrifugation procedure was used to separate VLDL from normal and uremic plasma samples. The levels of VLDL-cholesterol were measured directly and compared with the calculated values. Methods. Fasted blood samples were collected from 31 control subjects and 99 uremic patients and analyzed for total, free, and high density lipoprotein (HDL)-cholesterol. An aliquot from each plasma was used to prepare VLDL by a single preparative ultracentrifuge spin, using a Beckman type 25 rotor. Total cholesterol was measured in the VLDL samples and compared with the values calculated from the plasma triacylglycerol levels. Results. Measurement of VLDL-cholesterol after preparative ultracentrifugation in the type 25 rotor was reproducible. There were significant correlations between the measured and the calculated VLDL-cholesterol levels for both groups of plasma samples. However, calculated values were consistently 20%-40% higher than the measured values in both groups. Conclusions. The simple method for direct measurement of VLDL-cholesterol described here is easy and reproducible, and avoids overestimation of this parameter in uremic plasma samples.