Skip this step when checking lipid levels

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Skip this step when checking lipid levels

J Fam Pract. 2015 February;64(2):113-115

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References

1. Doran B, Guo Y, Xu J, et al. Prognostic value of fasting versus nonfasting low-density lipoprotein cholesterol levels on long-term mortality: insight from the National Health and Nutrition Examination Survey III (NHANES-III). Circulation. 2014;130:546-553.

2. Centers for Disease Control and Prevention (CDC). Vital signs: prevalence, treatment, and control of high levels of low-density lipoprotein cholesterol—United States, 1999-2002 and 2005-2008. MMWR Morb Mortal Wkly Rep. 2011;60:109-114.

3. Stone NJ, Robinson JG, Lichtenstein AH, et al; American College of Cardiology/American Heart Association Task Force on Practice Guidelines. 2013 ACC/AHA guideline on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk in adults: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63(25 pt B):2889-2934.

4. US Preventive Services Task Force. Final recommendation statement: Lipid disorders in adults (cholesterol, dyslipidemia): Screening. US Preventive Services Task Force Web site. Available at: http://www.uspreventiveservicestaskforce.org/Page/Document/ClinicalSummaryFinal/lipid-disorders-in-adults-cholesterol-dyslipidemia-screening. Accessed January 20, 2015.

5. National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 2002;106:3143-3421.

6. De Backer G, Ambrosioni E, Borch-Johnsen K, et al; European Society of Cardiology, American Heart Association. American College of Cardiology. European guidelines on cardiovascular disease prevention in clinical practice. Third Joint Task Force of European and other Societies on Cardiovascular Disease Prevention in Clinical Practice (constituted by representatives of eight societies and by invited experts). Atherosclerosis. 2004;173:381-391.

7. Genest J, McPherson R, Frohlich J, et al. 2009 Canadian Cardiovascular Society/Canadian guidelines for the diagnosis and treatment of dyslipidemia and prevention of cardiovascular disease in the adult - 2009 recommendations. Can J Cardiol. 2009;25:567-579.

8. Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972;8:499-502.

9. Sidhu D, Naugler C. Fasting time and lipid levels in a community-based population: a cross-sectional study. Arch Intern Med. 2012;172:1707-1710.

10. Langsted A, Nordestgaard BG. Nonfasting lipids, lipoproteins, and apolipoproteins in individuals with and without diabetes: 58,434 individuals from the Copenhagen General Population Study. Clin Chem. 2001;57:482-489.

11. Mora S, Rifai N, Buring JE, et al. Comparison of LDL cholesterol concentrations by Friedewald calculation and direct measurement in relation to cardiovascular events in 27,331 women. Clin Chem. 2009;55:888-894.

12. Gillespie CD, Keenan NL, Miner JB, et al; Centers for Disease Control and Prevention (CDC). Screening for lipid disorders among adults—National Health and Nutrition Examination Survey, United States, 2005-2008. MMWR Morb Mortal Wkly Rep. 2012;61 suppl:26-31.

13. Centers for Disease Control and Prevention. National Health and Nutrition Examination Survey. Centers for Disease Control and Prevention Web site. Available at: http://www.cdc.gov/nchs/nhanes/nh3data.htm. Accessed October 13, 2014.

14. Hosmer DW, Lemeshow S. Applied Logistic Regression. 2nd ed. New York, NY: John Wiley & Sons; 2000.

As expected, compared to individuals in the first LDL tertile (<100 mg/dL), those with a higher LDL had an increased risk of all-cause mortality (hazard ratio [HR]=1.61; 95% confidence interval [CI], 1.25-2.08 [second tertile] and HR=2.10; 95% CI, 1.70-2.61 [third tertile]). The prognostic value of fasting vs nonfasting status for predicting all-cause mortality was similar, as suggested by the C-statistics (0.59 [95% CI, 0.56-0.61] vs 0.58 [95% CI, 0.56-0.60]; P=.73).

The risk of cardiovascular mortality also increased with increasing LDL tertiles. As was the case with all-cause mortality, the prognostic value of fasting vs nonfasting status was similar for predicting cardiovascular mortality as observed by similar C-statistics (0.64 [95% CI, 0.62-0.66] vs 0.63 [95% CI, 0.60-0.65]; P=.49). In addition, fasting vs nonfasting C-statistics were similar for both diabetic and non-diabetic patients.

WHAT’S NEW: Results suggest fasting may no longer be necessary

While obtaining a fasting lipid panel is recommended by multiple guidelines and has become traditional practice, the need for fasting originated primarily out of concern for the effect of postprandial triglycerides on calculating LDL. This is the first study that compared the prognostic value of fasting and nonfasting LDL values for predicting mortality; it demonstrated that they are essentially the same.

CAVEATS: Fasting and nonfasting measurements were taken from different patients

The only challenge: It may be difficult for physicians to change a longstanding practice of checking fasting lipid profiles.The fasting and nonfasting lipids were not collected from the same individuals. However, to decrease confounding, Doran et al¹ factored in multiple cardiovascular risk factors as covariables.

Another caveat is that individuals with triglyceride levels >400 mg/dL were excluded. However, investigators ran a sensitivity analysis that included individuals with triglycerides >400 mg/dL and found no significant difference in C-statistics between the fasting and nonfasting groups.

CHALLENGES TO IMPLEMENTATION: Dropping the requirement to fast goes against established practice

It may be difficult for physicians to change a longstanding practice of checking fasting lipid profiles, but we see no other barriers to adopting this recommendation.

* The C-statistic is the probability that predicting the outcome is better than chance and is used to compare the goodness of fit of logistic regression models. Values for this measure range from 0.5 to 1.0. A value of 0.5 indicates that the model is no better than chance at making a prediction of membership in a group and a value of 1.0 indicates that the model perfectly identifies those within a group and those not.

ACKNOWLEDGEMENT
The PURLs Surveillance System was supported in part by Grant Number UL1RR024999 from the National Center For Research Resources, a Clinical Translational Science Award to the University of Chicago. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center For Research Resources or the National Institutes of Health.

References

9. Sidhu D, Naugler C. Fasting time and lipid levels in a community-based population: a cross-sectional study. Arch Intern Med. 2012;172:1707-1710.

14. Hosmer DW, Lemeshow S. Applied Logistic Regression. 2nd ed. New York, NY: John Wiley & Sons; 2000.

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