No Need to Fast Before Cholesterol Blood Test: Study

MONDAY Nov. 12, 2012 -- Current practice calls for patients to fast at least eight hours before having their cholesterol levels checked, but Canadian researchers report that may be unnecessary.

"For routine screening, fasting for cholesterol is largely unnecessary," because it has only a slight effect on test results, said lead researcher Dr. Christopher Naugler, assistant professor of clinical pathology at the University of Calgary, in Canada. "Eliminating fasting as a general requirement for cholesterol testing could greatly increase convenience for patients without significantly altering test results."

There are some patients, however, such as those with abnormally high triglycerides, where a repeat fasting cholesterol measurement may be necessary, Naugler said.

The report was published in the Nov. 12 online edition of the journal Archives of Internal Medicine.

For the study, Naugler and his colleague Dr. Davinder Sidhu looked at laboratory data on cholesterol tests from more than 200,000 patients.

The researchers compared fasting time with resulting cholesterol levels. Overall, they found fasting time made little difference in the accuracy of the blood test. Levels of total and HDL (good) cholesterol varied less than 2 percent with different fasting times.

In addition, levels of LDL (bad) cholesterol varied less than 10 percent and levels of triglycerides, a marker linked with inflammation, varied less than 20 percent, the researchers noted.

"In our opinion, physicians and health care providers may consider doing non-fasting lipid tests based on the current evidence," said Dr. Samia Mora, assistant professor of medicine at Brigham and Women's Hospital in Boston and co-author of an accompanying journal commentary.

Either non-fasting or fasting blood tests may be used for cholesterol testing, Mora said.

"This is based on a growing body of evidence -- including the present study, but also several other recent studies -- that non-fasting lipids are generally not substantially affected by the fasting," she said.

Non-fasting cholesterol blood tests have many advantages, Mora said.

"It's easier for patients, as it usually saves them from coming a second time after fasting. It's easier for physicians as well, as they can have the results faster," she said. "And it may potentially save costs, as sometimes individuals may have to repeat a blood test just for lipids if they weren't fasting the first time."

Another expert noted that non-fasting test results may also be a more reliable predictor of heart trouble.

"While most guidelines recommend obtaining a cardiovascular lipid panel after at least eight hours of fasting, many studies suggest for most individuals a non-fasting lipid panel provides similar lipid values," said Dr. Gregg Fonarow, associate director of the cardiology division at the University of California, Los Angeles. "Some analyses have even suggested that non-fasting lipid levels are more accurate for predicting the risk of cardiovascular events compared to those obtained in the fasting state."

More information

For more information on cholesterol, visit the American Heart Association.

Posted: November 2012


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