Detection of abnormal lipoproteins using Friedewald formula and data assurance of four lipid profiles

Abstract

Low-density lipoprotein cholesterol (LDL-C) estimates can be calculated on the basis of the levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG). Using the Friedewald formula, we calculated LDL-C as follows: LDL-C = (TC) − (HDL-C) − (TG/5). In most patients, the difference between TC level and HDL-C, LDL-C, and TG levels multiplied by 0.15 converges to a value of around 0 mg/dL. However, some cases show differences deviating significantly from this value. In the present study, we randomly selected patients who had their lipid profile (TC, HDL-C, LDL-C, and TG) examined between December 2019 and November 2021 and whose TC level difference ranged beyond (n = 58) and within (n = 8) 0 ± 25 mg/dL. Lipid patterns were examined by the electrophoretic analysis of lipoproteins based on the Chol/TG and LipoPhor system to measure the levels of phospholipids and free cholesterol. Of the 48 patients whose TC level difference was above ±25 mg/dL, the results indicated the presence of lipoprotein-X (LP-X) in 16 patients and either LP-X or LP-Y in 19 patients. Slow-alpha was identified in the serum of one patient, and the presence of abnormal lipoproteins could not be confirmed in 12 patients. The TG level was over 300 mg/dL in all 10 patients whose TC level difference was below 25 mg/dL. A TC level difference above ±15 mg/dL also contributed to the measurement failures and the detection of abnormal HDL-C in other patients. Our findings indicate that monitoring of the TC level difference not only contributes to the detection of abnormal lipoproteins but also in guaranteeing the quality of data on the four lipid profiles.