Fasting before lipid tests not necessary

Fasting before lipid tests not necessary
Fasting before lipid tests not necessary

Fasting prior to a routine cholesterol check may not be necessary, results from a large community-based population study suggest.

Overall mean cholesterol subclass levels differed little between people with various fasting time -- varying less than 2% for total cholesterol and high density lipoprotein (HDL) cholesterol, less than 10% for calculated low density lipoprotein (LDL) cholesterol, and less than 20% for triglycerides, Christopher Naugler, MSc, MD, of the University of Calgary in Alberta, and colleagues, reported in the Archives of Internal Medicine.

"This finding suggests that fasting for routine lipid level determinations is largely unnecessary," the researchers wrote. They added that fasting for routine blood work "presents an inconvenience for patients and may discourage compliance with routine screening programs."

The study included 209,180 men and women from Calgary, Alberta, who had at least one lipid profile completed during a 6-month period in 2011. Mean participant age was 53 years.

Mean total cholesterol at baseline was 183.4 mg/dL, mean HDL cholesterol was 55.2 mg/dL, mean LDL cholesterol 103.3 mg/dL and mean triglycerides 127.6 mg/dL.



Few statistically significant differences in cholesterol subclass levels were observed for fasting intervals when compared with either a 9- to 12-hour fasting time or a greater than 8-hour fasting time, the researchers found.

For example HDL cholesterol and calculated LDL levels were no different among men who fasted for 1 to 13 hours and those who fasted 14 to 15 hours, but there was a statistical difference between these fasting times and men who fasted 9 to 12 hours. Among women, 1 and 2 hour fasting resulted in significant statistical differences in total cholesterol and calculated LDL cholesterol compared with fasting for more than 8 hours.

In an invited commentary, Amit Khera, MD, and Samia Mora, MD, MHS, of Brigham and Women's Hospital in Boston, praised the study as one of the largest in North America to examine fasting versus nonfasting before cholesterol testing.

"Lipid testing plays a major role in cardiovascular risk stratification and the assessment of lipid responses to clinical interventions," Khera and Mora wrote. "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."

Although study findings show that total cholesterol and HDL cholesterol levels do not vary considerably by fasting time, J. Michael Gaziano, MD, MPH, of Brigham and Women's Hospital in Boston, wrote in an accompanying editorial that a different approach may be necessary for measuring triglycerides, which are more closely related to fasting times.

They study researchers acknowledged several limitations, including the relatively low mean age of the study cohort, low mean total cholesterol levels at baseline and the potential for recall errors due to self reported fasting times. Also, the study did not assess apolipoprotein A-1 or B-100, and did not ascertain whether patients were taking lipid lowering medications.


References

  1. Sidhu D et al. Arch Intern Med. 2012; DOI: 10.1001/archinternmed.2012.3708.
  2. Khera AV, Mora A. Arch Intern Med. 2012; DOI: 10.1001 /2013.jamainternmed.263.
  3. Gaziano JM/ Arch Intern Med 2012; DOI: 10.1001 /jamainternmed.2013.1771.
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