Low-density Lipoprotein Cholesterol Measurement Using the Direct Method Versus the Friedewald Equation, and the Clinical Background

Abstract

Aim: We aimed to compare the low-density lipoprotein cholesterol (LDL-c) values obtained by direct measurement (D) and by the Friedewald equation (F), and examine the validity of the LDL-c + 30 mg/dL value as a non-high-density lipoprotein cholesterol (non-HDL-c) reference value. Additionally, we evaluated the association between the discrepancies between D and F and the clinical background. Methods: We collected 2,237 samples from patients ≥ 20 year-old, in either fasting or non-fasting state. Results: The Spearman's correlation coefficient between D and F was 0.964 and there was a correlation between LogD and LogF (R2 = 0.9259). The average of % Bias was -4.94% in TG < 400 mg/dL. A weak correlation between non-HDL-c and D + 30 was observed in TG ≥ 400 mg/dL (R2 = 61%). In the most cases with D lower than F, end-stage liver disease was observed. In the cases with D higher than F, no particular diseases were observed. Conclusion: In conclusion, a significant correlation was found between D and F. Both D and F could be continuously compared and examined as follow-up data in TG < 400 mg/dL. We proposed to reconsider LDL-c + 30 mg/dL as a reference value of non-HDL-c in TG ≥ 400 mg/dL.

Keywords

• low-density lipoprotein cholesterol
• direct ldl-c assay
• friedewald equation