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Comment & Response
September 30, 2020

Accuracy of New Equation to Calculate Low-Density Lipoprotein Cholesterol—Reply

Author Affiliations
  • 1Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
  • 2Clinical Center, Department of Laboratory Medicine, National Institutes of Health, Bethesda, Maryland
JAMA Cardiol. 2021;6(1):122-123. doi:10.1001/jamacardio.2020.4445

In Reply We thank Muthukumar et al and Martin et al on their insightful comments about our new equation for more accurately calculating low-density lipoprotein cholesterol (LDL-C) levels,1 which can be freely downloaded.2 We agree that monitoring long-term drifts in any assay is important for ensuring accuracy. Our results for the β-quantification test, which is the reference method for LDL-C and is what we used to develop our equation, were closely monitored throughout the 23-year period that data were collected for our study. During this time, we participated in the semiannual US Centers for Disease Control and Prevention Lipid Standardization Program and thus were able to make sure, using split samples, that our assay was traceable to the β-quantification test performed by the Centers for Disease Control and Prevention, which is routinely used by diagnostic companies to calibrate their lipid assays. We also agree that our equation does not perform as well on samples with high triglyceride levels (greater than 400 mg/dL [to convert to millimoles per liter, multiply by 0.0113]), but it does perform significantly better than the Friedewald or other equations on such samples. It showed an accuracy advantage compared with other LDL-C equations in patients with triglyceride levels greater than approximately 300 mg/dL. We recommend a triglyceride level cut point of 800 mg/dL for no longer using our new equation. At this point, the new equation becomes as inaccurate as the Friedewald equation is at a triglyceride level of 400 mg/dL, the traditional cut point used for no longer calculating LDL-C levels.

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