Research News

Is fasting necessary before lipid tests?

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e7662 (Published 14 November 2012) Cite this as: BMJ 2012;345:e7662

It may be unnecessary to fast before tests for serum lipids, say researchers from Canada. In a cross sectional analysis of more than 209 180 results, fasting times made little difference to concentrations of total cholesterol and high density lipoprotein cholesterol. Concentrations of low density lipoprotein cholesterol varied by no more than 10% in adults who reported fasting for one to 16 hours. Triglyceride concentrations varied by no more than 20%.

The authors analysed men and women separately and adjusted for age. They weren’t able to account for drug treatments, or for the content of each person’s last meal. All fasting times were self reported.

Fasting for nine to 12 hours before a routine blood test is unpleasant and inconvenient, says a linked comment (doi:10.1001/2013.jamainternmed.263). Some people default and others are left in long queues at morning phlebotomy sessions, where most fasting tests are done. The new analysis isn’t definitive but does add to growing evidence that lipid tests done without fasting may be a viable alternative. It would be reasonable to offer a non-fasting test to most people presenting to routine clinics. But we shouldn’t abandon fasting tests altogether until we have better prospective studies comparing the clinical value of fasting and non-fasting tests more directly. Most research underpinning current practice was done using fasting tests. We need more reassurance that the non-fasting option is just as good for predicting cardiovascular disease and informing therapeutic decisions.

Notes

Cite this as: BMJ 2012;345:e7662