Written by Dr David Deam
Recent evidence is challenging the need to have patients fast for blood tests when assessing for risk of cardiovascular disease.
It has now been shown that non-fasting triglycerides are superior to fasting in predicting cardiovascular risk. Patients usually eat regularly during the day with the fasting state only occurring shortly before breakfast; a lipid profile measured during this time may not accurately reflect the lipid concentration during the day. In addition, lipids and lipoproteins only change minimally in response to normal food intake; for instance, in four large prospective studies, there was minimal change in triglyceride levels in patients who had a non-fasting versus a fasting blood test.(1, 2) Further, in results from a population of 108,602, patients who had non-fasting random blood tests and had the highest lipid results (including triglycerides) had the highest risk of ischaemic heart disease (IHD).(3) Finally, results from studies assessing the effectiveness of lipid-lowering agents, using non-fasting samples, show that reducing the levels of non-fasting lipids reduced the risk of cardiovascular disease.(4)
There is no sound scientific evidence as to why fasting should be superior to non-fasting when evaluating a lipid profile for cardiovascular risk prediction. Non-fasting tests simplify blood tests in the laboratory, avoid the inconvenience of fasting tests and prevent the clinical risk associated with fasting blood tests in patients with diabetes who may be at risk of iatrogenic hypoglycaemia. The scientific evidence suggests that we should move away from fasting blood tests, despite the fact that this is the way it has always been done; fortunately, guidelines are being modified to reflect these changes.(5, 6)
In Summary
1. Lipids only differ slightly in fasting versus non-fasting tests
2. Non-fasting triglycerides are better at predicting cardiovascular risk
3. Studies of lipid-lowering agents using non-fasting tests showed reducing levels of non fasting lipids correlated with reduced risk of cardiovascular disease
4. Non-fasting lipids are more convenient and safer for patients (particularly for diabetics)
5. Guidelines are currently being updated to reflect the above
References
1. Langsted A, Nordestgaard BG. Nonfasting versus fasting lipid profile for cardiovascular risk prediction. Pathology. 2019;51(2):131-41.
2. Langsted A, Freiberg JJ, Nordestgaard BG. Fasting and nonfasting lipid levels: influence of normal food intake on lipids, lipoproteins, apolipoproteins, and cardiovascular risk prediction. Circulation. 2008;118(20):204756.
3. Nordestgaard BG, Langsted A, Mora S, Kolovou G, Baum H, Bruckert E, et al. Fasting Is Not Routinely Required for Determination of a Lipid Profile: Clinical and Laboratory Implications Including Flagging at Desirable Concentration Cutpoints-A Joint Consensus Statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine. Clin Chem. 2016;62(7):930-46.
4. Heart Protection Study Collaborative G. MRC/BHF Heart Protection Study of cholesterol lowering with simvastatin in 20,536 high-risk individuals: a randomised placebo-controlled trial. Lancet. 2002;360(9326):722.
5. Miller M, Stone NJ, Ballantyne C, Bittner V, Criqui MH, Ginsberg HN, et al. Triglycerides and cardiovascular disease: a scientific statement from the American Heart Association. Circulation. 2011;123(20):2292-333.
6. Anderson TJ, Gregoire J, Pearson GJ, Barry AR, Couture P, Dawes M, et al. 2016 Canadian Cardiovascular Society Guidelines for the Management of Dyslipidemia for the Prevention of Cardiovascular Disease in the Adult. Can J Cardiol. 2016;32(11):1263-82
About the author
Dr David Deam
MBBS, MAACB, FRCPA
Lab: Clayton
Areas Of Interest: Endocrine Function
Testing, Protein Abnormalities,
Laboratory Automation
Speciality: Chemical Pathology
Phone: 03) 9538 6777
Email: david.deam@clinicallabs.com.au
Dr Deam graduated with Honours in Medicine from Monash University in 1978 and obtained his FRCPA in 1985, following postgraduate training in Biochemistry at the Royal Melbourne Hospital. After several posts in Chemical Pathology at the Royal Melbourne Hospital and the Royal Women’s Hospital, he was appointed Head of Chemical Pathology at the Royal Melbourne in 1996. He joined Gribbles Pathology (now Australian Clinical Labs) in 1998. Dr Deam has played an active role in teaching scientific, nursing and medical staff at both undergraduate and postgraduate levels and has been an examiner for the Australasian Association of Clinical Biochemists as well as the Royal College of Pathologists of Australasia. Dr Deam’s research interests and publications include work on thyroid function testing, various aspects of diagnostic protein measurement and the rational use of biochemical tests.
