MEASUREMENT OF LDL PARTICLE-SIZE IN WHOLE PLASMA AND SERUM BY HIGH-PERFORMANCE GEL-FILTRATION CHROMATOGRAPHY USING A FLUORESCENT LIPID PROBE

We have recently described a technique for measuring LDL size by high performance gel-filtration chromatography (HPGC) with UV detection (Sc heffer et al., Clin Chem 1997;43:1904-12). A drawback of this method i s the necessity of LDL isolation before chromatography. We now describ e a modification of this method based on selective detection of lipopr oteins by postcolumn labeling with parinaric acid, a fluorescent lipid probe. Measuring the size of isolated LDL by HPGC in 56 subjects, we obtained diameters of 25.72 +/- 0.60 nm with UV detection and of 25.74 +/- 0.58 nm with fluorescence detection. The modified method is suita ble for LDL size measurement in whole plasma or serum. LDL sizes measu red in whole plasma correlated strongly with the respective values in isolated LDL (r = 0.976) but were on average 0.18 nm larger (P < 0.001 ). CVs for within- and between-series imprecision were < 0.25%. The pr esent method requires only 5 mu L plasma or serum without sample prepa ration and is suitable for the unattended analysis of large series of samples.