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Fasting makes little difference to results of lipid tests

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e7806 (Published 16 November 2012) Cite this as: BMJ 2012;345:e7806
  1. Lilian Anekwe
  1. 1BMJ Evidence Centre

Fasting before routine lipid level tests might be unnecessary, suggests a study that found that fasting time had little association with lipid subclass levels in a large population.

The researchers, from Calgary in Alberta, Canada, looked at the relationship between fasting duration and lipid test results over a six month period in 2011 in 209 180 people.

They found that among average cholesterol levels the mean levels of total cholesterol and high-density lipoprotein (HDL) differed little among individuals with various fasting times.1 Specifically, these levels varied by less than 2% for total cholesterol and HDL cholesterol, by less than 10% for calculated low density lipoprotein (LDL) cholesterol, and by less than 20% for triglycerides.

The only significant differences among the subclasses were present for a minority of fasting intervals when compared with fasting times over eight hours. For example, among men, triglyceride levels obtained after between one and six hours of fasting were significantly different from those obtained after eight or more hours of fasting, with a similar finding among women.

The authors conclude that their findings suggest “that fasting for routine lipid level determinations is largely unnecessary.”

They add that people with an initial triglyceride level higher than 400 mg/dL might need to be followed up with a fasting lipid level test or direct measurement of LDL cholesterol levels or both.

Future studies might need to examine a number of lipid level tests in the same people after different fasting times, they suggest.

In an accompanying editorial, J Michael Gaziano of Brigham and Women’s Hospital, Harvard Medical School, and VA Boston Healthcare System, writes: “Most of the reasons that we measure a lipid profile depend on total and HDL cholesterol levels. 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, the laboratories, and our ability to provide timely counselling to our patients. This, in my opinion, tips the balance toward relying on non-fasting lipid profiles as the preferred practice.”2

However, in a commentary, Amit Khera and Samia Mora of Brigham and Women’s Hospital and Harvard Medical School, Boston, say, “Further validation studies are needed before a non-fasting lipid testing strategy is universally endorsed.”3

Notes

Cite this as: BMJ 2012;345:e7806

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