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Fasting may not be necessary before cholesterol test, study finds

REUTERS/Luis Galdamez
A new study's authors found that fasting times made little difference in cholesterol test results.

Most people do not need to undergo a nine-hour fast to get accurate results from a cholesterol-screening blood test, suggests a Canadian study published Monday in the Archives of Internal Medicine.

If these findings hold up, they may have a significant impact on the number of people who undergo cholesterol screening. Many people skip having their cholesterol checked because of the inconvenience of having to fast beforehand. The National Heart Lung and Blood Institute currently recommends at least nine hours of fasting to ensure reliable results for a full cholesterol, or lipid, profile.

The new study involved 209,180 individuals who had their cholesterol levels tested in 2011. The participants were asked how long they had fasted before the test, with the answers ranging from one to 16 hours.

After crunching all the data, the study’s authors found that fasting times made little difference in test results. For total cholesterol and high-density lipoprotein (HDL) cholesterol the difference was, on average, less than 2 percent. For low-density lipoprotein (LDL) cholesterol, the difference was less than 10 percent. And for triglycerides it was less than 20 percent.

“This finding suggests that fasting for routine lipid level determinations [is] largely unnecessary,” the authors concluded.

As one of the authors, Dr. Christopher Naugler of Calgary University, explained to New York Times reporter Nicholas Bakalar, “The ones that varied the least — HDL and total cholesterol — are the ones that matter the most in estimating risk for cardiovascular problems. It may even be that knowing a lipid level in a nonfasting state is a better way to estimate risk. No one knows yet.”

In an editorial that accompanied the study, Dr. J. Michael Gaziano, a professor of medicine at Harvard Medical School, agreed that the study’s findings suggest that most people don’t need to fast to get useful cholesterol measurements (known in medical lingo as a lipid profile):

[I]n practice, you can begin with a nonfasting lipid profile, and it is possible to use nonfasting levels for risk assessment, decisions about initiating treatment, and monitoring the effects of treatment. If you want to monitor triglyceride levels, then doing some sample fasting may useful. With this approach, most of our lipid profiles can be obtained in the nonfasting state, increasing convenience for our patients and ourselves and decreasing the burden on the laboratory, with no real adverse effect on clinical decision making.

You can read the study on the Archives website. The editorial, unfortunately, is behind a paywall is also available for free on the site.

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Comments (1)

  1. Submitted by Ray Schoch on 11/14/2012 - 12:40 pm.


    There may be medical reasons why a 12-hour fast before a “lipid profile” blood might be something to avoid, but “inconvenience” doesn’t strike me as one of them.

    Maybe if I had the blood draw done at 2 PM a 12-hour fast WOULD be inconvenient, and there must be some people for whom that’s more the norm than the exception, but since I’m the one scheduling the appointment to have it done, I’ve always scheduled it for relatively early morning (e.g., 8:00 AM). It takes only a few minutes, so my usual breakfast is merely delayed for a bit, rather than skipped altogether.

    Still, I hope there’s enough follow-up with replicable results to persuade my doctor (and most others) that this initial suggestion can be followed. I certainly won’t mind not having to fast.

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