Practical differences between three equations for estimating low‐density lipoprotein‐cholesterol (LDL-C)

Research Objectives: Low-density lipoprotein-cholesterol (LDL-C) remains of utmost clinical importance as a treatment target and primary cholesterol target in the primary prevention of atherosclerotic cardiovascular disease. The United States and European Guidelines on dyslipidemia require follow-up testing of LDL-C to determine treatment adequacy and assess percent LDL-C lowering. This study aimed to examine the practical differences between three equations for estimating LDL-C: Friedewald, Martin/Hopkins, and NIH Equation 2 in individuals with TG < 400 mg/dL.

Design: This is an observational study.

Setting: General community.

Participants: Blood lipid measurements, taken from 4,617 noninstitutionalized participants, aged 12 to 80, were obtained from the National Health and Nutrition Examination Survey (NHANES) study. We (1) compared the practical differences in LDL-C estimates between three equations and illustrated the results using the Bland–Altman plot, (2) examined the correlations using the Pearson correlation coefficients, (3) developed the predicting equations using the simple regression, and (4) investigated the degree of agreement using weighted Kappa and computed the percentage of agreement.

Interventions: N/A

Main Outcome Measures: Blood lipid measurements.

Results: Overall, the mean differences between Martin/Hopkins and Friedewald LDL-C estimates were 0.74 in males, and -0.16 in females, respectively. The mean differences between NIH Equation 2 and Friedewald LDL-C estimates were 1.61 in males, and 1.41 in females, respectively. The correlations between Friedewald and other equations were high (r = 0.991 with Martin/Hopkins, and r = 0.998 with NIH Equation 2). The weighted Kappa coefficients between Friedewald and other equations were high (k = 0.931 Martin/Hopkins, and 0.956 with NIH Equation 2). The percentage of agreement in classifying individuals into the same LDL-C category was 93% between Friedewald and Martin/Hopkins, and 95.5% between Friedewald and NIH Equation 2.

Conclusions: Future studies are warranted to redefine LDL-C estimation methods as our treatment targets evolve and novel therapeutics progress.

Author(s) Disclosures: The authors declare no conflict of interest.