Different Methods of Low-density Lipoprotein Cholesterol Estimation and the Impact on Lipid-lowering Therapy in Patients with Coronary Artery Disease

BACKGROUND: Indirect estimation of low-density lipoprotein cholesterol (LDL-C) is a common clinical practice. The Friedewald equation is used most often but has inherent limitations. Clinical implications of such a practice have not been well defined, especially in the current era of targeting low (<50-70 mg/dL) or ultralow (<30-40 mg/dL) LDL-C levels. METHODS: Overall, 3,028 consecutive subjects with coronary artery disease (CAD) undergoing coronary revascularization were included. Four methods of LDL-C estimation were compared: direct estimation, the Friedewald, Martin, and Sampson equations. RESULTS: -values <0.001 for all the comparisons). Among patients with LDL-C >70 mg/dL and >50 mg/dL, the Friedewald equation erroneously classified 24.6% and 19.9%, respectively, as having LDL-C below these thresholds. This error increased with increasing triglyceride levels. The Martin equation was the most accurate, whereas the Sampson equation had intermediate accuracy. CONCLUSION: Our study shows that the Friedewald equation underestimates LDL-C and can potentially result in significant undertreatment in patients with CAD in whom aggressive LDL-C lowering is crucial. Direct estimation is the preferred method, but the Martin equation could be a reasonable alternative if the direct estimation is not feasible due to logistical constraints.