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Word of the Day

Fasting not necessary before lipid panels

Clinical Question:
Do patients have to fast before obtaining a lipid panel?

Bottom Line:
Forget fasting as a requirement for cholesterol screening or monitoring. Cholesterol levels, with the exception of triglycerides, are similar when drawn after fasting or soon after a meal. Even triglyceride levels will be elevated by less than 20% if the patient has not fasted. Similarly, hemoglobin A1c determinations for the diagnosis or monitoring of type 2 diabetes can be drawn at the visit regardless of a recent meal (Diabetes Care 2012;35 Suppl 1:S11-63). If you get some push back from your lab tech, ask him or her to fast until 10:30 some morning, which is what I had to do before my last visit. The resulting grumpiness may generate some empathy. (LOE = 2b)

Reference:
Sidhu D, Naugler C. Fasting time and lipid levels in a community-based population. A cross-sectional study. Arch Intern Med 2012;Nov 12:1-4 [Epub ahead of print].  [PMID:23147400]

Study Design:
Cross-sectional

Funding:
Self-funded or unfunded

Setting:
Population-based

Synopsis:
These Canadian investigators looked at lipid levels for 209,180 individuals (111,048 women and 98,132 men), which comprised all the lipid panels reported for a 6-month period in Calgary (a single laboratory provides all testing for the city). The authors also recorded, as a matter of practice, the length of time of the fast before blood was drawn. The huge number of patients should present an average with only small variation (confidence interval); as a result, any differences found by stratifying results by the duration of the fast should indicate an effect of recent food ingestion on measurements. Although the majority of serum levels were drawn after at least 10 hours of fasting, the average result was remarkably similar when compared across hours of fasting. The mean cholesterol levels varied by less than 2% for total cholesterol and high-density lipoprotein cholesterol, by less than 10% for calculated low-density lipoprotein cholesterol, and by less than 20% for triglycerides over the fasting times.

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