Evaluation of an HPLC method for LDL-cholesterol determination in patients with various lipoprotein abnormalities in comparison with beta-quantification

Background: The main purpose of this study was to evaluate an HPLC method for LDL-cholesterol determination in the presence of abnormal lipoproteins. Methods: We compared LDL-cholesterol levels obtained by HPLC (HPLC-LDL), Friedewald (F-LDL), and β-quantification (BQ-LDL) methods on 47 healthy volunteers and 50 outpatients with lipid disorders, including apolipoprotein E2/2 phenotype, cholesteryl ester transfer protein deficiency and lipoprotein lipase deficiency. Results: For the control group (n = 50), the HPLC-LDL and the F-LDL correlated highly with the BQ-LDL (r = 0.984 and 0.969, respectively), but the HPLC-LDL was lower than the BQ-LDL (mean bias: - 4.0%, P < 0.001). For the subjects with lipoprotein abnormalities, significant biases were found in HPLC-LDL for the hypertriglyceridemia (+ 25%, n = 17, P < 0.01), the hyper HDL (- 15.2%, n = 10, P < 0.01) and the hyper lipoprotein(a) groups (- 13.4%, n = 12, P < 0.001). The F-LDL was significantly higher than the BQ-LDL in the apolipoprotein E2/2 subjects (+ 92%, n = 8, P < 0.001), but not significantly different in other subjects with triglycerides < 4000 mg/l. Conclusions: There were several discrepancies in LDL-cholesterol levels determined by the HPLC and the BQ methods in samples with lipoprotein abnormalities. However, the HPLC method can be useful and informative for analysis of abnormal lipoproteins.