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J Am Coll Cardiol. 2013 Aug 20;62(8):732-9. doi: 10.1016/j.jacc.2013.01.079. Epub 2013 Mar 21.

Friedewald-estimated versus directly measured low-density lipoprotein cholesterol and treatment implications.

Author information

1
Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, Baltimore, Maryland 21287, USA. smart100@jhmi.edu

Abstract

OBJECTIVES:

The aim of this study was to compare Friedewald-estimated and directly measured low-density lipoprotein cholesterol (LDL-C) values.

BACKGROUND:

LDL-C is routinely estimated by the Friedewald equation to guide treatment; however, compatibility with direct measurement has received relatively little scrutiny, especially at levels <70 mg/dl now targeted in high-risk patients.

METHODS:

We examined 1,340,614 U.S. adults who underwent lipid profiling by vertical spin density gradient ultracentrifugation (Atherotech, Birmingham, Alabama) from 2009 to 2011. Following standard practice, Friedewald LDL-C was not estimated if triglyceride levels were ≥ 400 mg/dl (n = 30,174), yielding 1,310,440 total patients and 191,333 patients with Friedewald LDL-C <70 mg/dl.

RESULTS:

Patients were 59 ± 15 years of age and 52% were women. Lipid distributions closely matched those in the National Health and Nutrition Examination Survey. A greater difference in the Friedewald-estimated versus directly measured LDL-C occurred at lower LDL-C and higher triglyceride levels. If the Friedewald-estimated LDL-C was <70 mg/dl, the median directly measured LDL-C was 9.0 mg/dl higher (5th to 95th percentiles, 1.8 to 15.4 mg/dl) when triglyceride levels were 150 to 199 mg/dl and 18.4 mg/dl higher (5th to 95th percentiles, 6.6 to 36.0 mg/dl) when triglyceride levels were 200 to 399 mg/dl. Of patients with a Friedewald-estimated LDL-C <70 mg/dl, 23% had a directly measured LDL-C ≥ 70 mg/dl (39% if triglyceride levels were concurrently 150 to 199 mg/dl; 59% if triglyceride levels were concurrently 200 to 399 mg/dl).

CONCLUSIONS:

The Friedewald equation tends to underestimate LDL-C most when accuracy is most crucial. Especially if triglyceride levels are ≥ 150 mg/dl, Friedewald estimation commonly classifies LDL-C as <70 mg/dl despite directly measured levels ≥ 70 mg/dl, and therefore additional evaluation is warranted in high-risk patients.

KEYWORDS:

Friedewald equation; HDL-C; LDL-C; NHANES; National Health and Nutrition Examination Survey; VAP; VLDL-C; Vertical Auto Profile; high-density lipoprotein cholesterol; low-density lipoprotein cholesterol; very low density lipoprotein cholesterol

Comment in

PMID:
23524048
DOI:
10.1016/j.jacc.2013.01.079
[Indexed for MEDLINE]
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