Eating Before Lipid Test OK

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It may not be necessary to fast before a routine cholesterol check, a large community-based population study suggested.

Overall, the mean cholesterol subclass levels varied by less than 2% for total cholesterol and high density lipoprotein (HDL) cholesterol, by less than 10% for calculated low density lipoprotein (LDL) cholesterol, and by less than 20% for triglycerides, reported Christopher Naugler, MSc, MD, of the University of Calgary in Alberta, and colleagues.

"This finding suggests that fasting for routine lipid level determinations is largely unnecessary," they said in the Nov. 12 Archives of Internal Medicine.

The finding is not new and corroborates results from smaller observational studies.

Naugler and colleagues noted that fasting is inconvenient for patients and "may discourage compliance with routine screening programs."

They also suggested that eating before cholesterol testing can highlight insulin resistance, which is "associated with worse postprandial lipid or lipoprotein clearance." In addition, high triglyceride levels after eating are "excellent predictors of insulin resistance."

For the study, investigators included 209,180 individuals who had at least one lipid profile completed during a 6-month period in 2011.

Participants were from Calgary, Alberta, and their mean age was 53. Slightly more than half (53%) were women. The mean total cholesterol at baseline was 183.4 mg/dL, the HDL cholesterol was 55.2 mg/dL, the LDL cholesterol 103.3 mg/dL, and triglycerides 127.6 mg/dL.

A policy change at the testing laboratory allowed the processing of patient samples irrespective of the duration of fasting times. However, the fasting times had to be recorded in the laboratory report, researchers wrote.

The researchers found only a few statistically significant differences among cholesterol subclass levels for fasting intervals when compared with either a 9- to 12-hour fasting time or a greater than 8-hour fasting time.

For example, in men fasting 14 and 15 hours, total cholesterol, HDL cholesterol, and calculated LDL cholesterol were significantly different from the 9- to 12-hour fasting time, but from 1 to 13 hours did not differ.

In women, the total cholesterol and calculated LDL cholesterol at 1 and 2 hours of fasting were significantly different than both the 9- to 12-hour fasting time and greater than the 8-hour time.

"So how does this help our physician? The fact that total and HDL cholesterol values vary little is quite useful," wrote J. Michael Gaziano, MD, MPH, of Brigham and Women's Hospital in Boston, in an accompanying editorial.

Much of the value of a lipid profile is captured in total cholesterol and HDL cholesterol, which did not vary considerably, Gaziano said.

A different approach has to be considered if triglycerides are the focus of concern, as their levels are more tied to fasting levels, Gaziano noted.

"Lipid testing plays a major role in cardiovascular risk stratification and the assessment of lipid responses to clinical interventions," wrote Amit Khera, MD, and Samia Mora, MD, MHS, of Brigham and Women's Hospital in Boston, in an invited commentary.

"Current guidelines suggest that blood samples for lipid profiles should be obtained after a 9- to 12-hour fast. This requirement is not always practical for patients, who rarely present to healthcare providers in a fasting state," Khera and Mora said.

They noted that the relatively low mean age of this cohort (53) and low total cholesterol at baseline (183 mg/dL) might preclude these results from applying to higher risk patients. Despite this, they praised the study as one of the largest in North America to examine fasting versus nonfasting before cholesterol testing.

They also wrote that these results add to the growing body of evidence that patients need not fast before lipid blood draws.

Naugler and colleagues noted a limitation of the study was that meal contents were not known before blood draws. Also, there might have been recall errors for self-reported fasting times.

In addition, their analysis did not include cholesterol components such as apolipoprotein A-1 or B-100. They also did not know the status of who was or wasn't on lipid-lowering drugs.

From the American Heart Association

• Managing Abnormal Blood Lipids: A Collaborative Approach
• Triglycerides and Cardiovascular Disease