Fasting before lipid testing may no longer be necessary

By Sally Robertson, B.Sc.Nov 13 2012

It may no longer be necessary for patients to fast before having their lipid levels tested, show study findings.

"Fasting for routine lipid level determinations is largely unnecessary," report Christopher Naugler (University of Calgary, Canada) and colleagues in the Archives of Internal Medicine.

In a cross-sectional analysis of laboratory data collected over a 6-month period for 209,180 individuals, the researchers found that fasting duration (time since last meal), which was stratified by hourly intervals from 1 to 16 hours, showed no significant association with lipid subclass levels.

The mean cholesterol subclass level varied by less than 2% for total cholesterol and high-density lipoprotein (HDL) cholesterol, by less than 10% for low-density lipoprotein cholesterol, and by less than 20% for triglycerides.

Naugler et al say several other studies have recently suggested that the measurement of nonfasting lipid subclasses is an acceptable option, with some nonfasting markers actually superior to fasting markers for assessing risk for cardiac events.

"Furthermore, as humans are usually in a nonfasting state, nonfasting values may be more representative of usual metabolic conditions," they point out.

The researchers add that measuring lipid levels in a non-fasting state could help compliance, because the inconvenience of having to fast for routine blood tests often discourages patients from complying with screening programs. Also, because fasting blood work is often carried out in phlebotomy clinics, the large number of phlebotomies needed for lipid testing can result in long waiting times, further inconveniencing patients.

Naugler and colleagues say that their findings, when combined with the results of other recent studies, suggest that determining nonfasting lipid levels is a reasonable alternative to determining fasting ones.

In an accompanying editorial, Michael Gaziano (Harvard Medical School, Boston, USA) notes that "most of the reasons that we measure a lipid profile depend on total and HDL cholesterol levels for most of our decision making. The incremental gain in information of a fasting profile is exceedingly small for total and HDL cholesterol values and likely does not offset the logistic impositions placed on our patients."

He adds: "This, in my opinion, tips the balance toward relying on nonfasting lipid profiles as the preferred practice."

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