Comparison of Low-Density Lipoprotein Cholesterol Concentrations by Direct Measurement and by Friedewald Calculation

The purpose of this study was to compare Friedewald-calculated and directly measured low-density lipoprotein cholesterol (LDL-C) levels. LDL-C is routinely estimated by the Friedewald formula in clinical practice. However, unreliability of the Friedewald-calculated LDL-C appears at lower LDL-C level or high triglyceride levels. We examined 147,143 Korean adults who underwent a comprehensive health examination in 2017. After excluding subjects with calculated Friedewald LDL-C <0 and triglyceride levels ≥400 mg/dL, 145,043 subjects (female; 43%, mean age; 42 ± 8) were analyzed. Friedewald-calculated LDL-C levels were approximately 15 mg/dL lower to directly measured LDL-C. Friedewald measurement had high sensitivity (79.2%, 82.2% of sensitivity in males and 74.5% of sensitivity in females) and specificity (100%) for directly measured LDL-C cut-off value of ≥100 mg/dL in all levels of triglyceride. In 82% of total subjects, LCL-C measured by both methods differed by more than 10 mg/dL. The proportion of reclassification between both methods for National Cholesterol Education Program categories of risk was 50.3% of patients with Friedewald measurement of LDL-C <70 mg/dL, 68% had directly measured LDL-C ≥70 mg/dL. Direct and Freidewald measurements of LDL-C levels are well correlated. However, concordance of both methods is low and reclassification between both is substantial for NECP categories of risk. Thus, it is desirable to make a global consensus on the LDL-C measurement.