Progressing from Fasting to Non-Fasting Lipid Testing

Dr Alap Christy*, Dr Abhik Banerjee*, Dr Kshama Pimpalgaonkar* and Dr Arnab Roy^
Department of Biochemistry*, Research & Development^, SRL Limited, S. V. Road, Goregaon West, Mumbai 400062, India

Conventional lipid testing insists upon a fasting state; primarily due to influence of circulating triglycerides being responsible for assay interference and limitations of assays which have a certain degree of resistance to provide reliable results in non fasting sample. However, the quest has always been to simplify the healthcare needs as much as possible to reduce the amplitude of already existing illness and anxiety. Requirement of collection of sample in 8-12 hr fasting state causes a significant burden for some active people who hate to fast, people with diabetes, and children.

Lipid profile is a predictor of vascular health and has been proven to predict the risk of cardiovascular illnesses to a significant extent. NCEP [1] recommends a fasting sample for doing lipid profile for cardiovascular risk assessment. Lipids have traditionally been tested after a fast for two main reasons. The first was to minimize variation, since eating could affect some lipid levels. The second was to produce a better calculation of LDL-cholesterol, which was often derived from Friedwald equation thought to provide distorted results after eating. More recent clinical studies have largely negated these concerns. Total and HDL cholesterol are spared from fasting state as they are not much affected by the same, so is measurement of direct LDL. Also, non-HDL cholesterol a promising marker may also be used in the non-fasting state. Over the period of time there has been a notion of change in this practice.

According to a consensus statement from European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine, published recently in the prestigious European Heart Journal[2] fasting is not routinely required for determination of a lipid profile. Lipid testing in non-fasting sample has become the clinical standard in Denmark, based on recommendations from the Danish Society for Clinical Biochemistry wherein clinicians can opt to re-measure triglyceride concentrations in the fasting state if non-fasting values are >350 mg/dL[3,4]. Furthermore, the UK NICE guidelines also suggest practicing non-fasting lipid testing since 2014 in primary prevention settings [5]. In 2013, the American College of Cardiology and the American Heart Association recommended that non-fasting lipid tests can be used for assessing cardiovascular risk, but still recommended a fasting lipid panel prior to statin initiation.

non-fasting-cholesterol-test

The major advantages of using Non-fasting Lipid testing are:

  • It simplifies blood sampling for patients, laboratories and Doctors.
  • It is likely to improve patient compliance -as patients are often inconvenienced by having to return on a separate visit for a fasting lipid profile.
  • Laboratories are burdened with more number of patients in the morning hours, which in turn also lead to more waiting time and further lengthen the fasting period for the patients scheduled in later morning.
  • Doctors are burdened by having to review and make decisions on the basis of the lipid profile at a later date. This situation may also require an extra effort to the clinical staff in making phone calls and scheduling the next appointments[2]
  • Also a solid Evidence is lacking that fasting is superior to non-fasting when evaluating the lipid profile for cardiovascular risk assessment.

There are a few Limitations of a Non- Fasting Lipid testing: [2]

  • Fasting before lipid testing is believed to provide more standardized measurements because of a perception that diet affects circulating lipid levels.
  • There is a perception towards non-fasting lipid profiles being less accurate and may make calculation of low-density lipoprotein (LDL) cholesterol via the Friedewald equation invalid.
  • Since fasting has been the clinical standard, it is not clear what values should be flagged as abnormal when using non-fasting.

However, European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine concluded in their review that effect of diet on lipid profile was not as significant as was perceived earlier, and can be overcome by restricting or standardizing fluid intake especially in diabetic subjects; reason being LDL is affected by fluid intake in diabetics, however the risk of LDL being affected in such patients was very much negligible [2].

Also cardiovascular risk is associated with higher amount of lipids present on an average. This means if circulating lipids are more in blood after a diet, it actually increases the risk of cardiovascular events. Therefore lipid profile in fasting state may actually fail to give a true picture of cardiovascular health.

In the era of wide usage of Direct LDL, usage of Friedewald’s formula is likely to become obsolete very soon. In this case the 2nd limitation is easily overcome.

When it comes to risk stratification and decision of starting statins, recent approach is focused on LDL measurement, which is more or less stable in fasting or non fasting condition except in a few diabetics due to fluid restriction as mentioned earlier. A careful treatment decision can be taken in such cases.

Consensus is to bury the old and move ahead with newer, more practical yet, effective approaches. Using non-fasting blood samples for routine assessment of plasma lipid profiles may be one of those.

AUTHOR INFO


alap-christy

Dr Alap Christy, MD, Biochemist, Department of Biochemistry

abhik-banerjee

Dr Abhik Banerjee, MD, Pathologist, Department of Biochemistry

1212

Dr Kshama Pimpalgaonkar, MD, Biochemist, Department of Biochemistry

dr-arnab-roy_pic

Dr Arnab Roy, MD, Deputy General Manager, R&D

 

 

 

 

 

 

 


References:

1)Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) Circulation. 2002 Dec 17; 106(25):3143-421.

2) Børge G. Nordestgaard et al.Fasting is not routinely required for determinationof a lipid profile: clinical and laboratory implications including flagging at desirable concentration cut-points—a joint consensus statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine. European Heart Journal Advance Access published April 26, 2016.doi:10.1093/eurheartj/ehw152

3)Nordestgaard BG, Hilsted L, Stender S. Plasmalipider hos ikkefastende patienter og signalværdier pa° laboratoriesvar. Ugeskr Laeger 2009;171:1093.

4) Langsted A, Nordestgaard BG. Nonfasting lipids, lipoproteins, and apolipoproteins in individuals with and without diabetes: 58 434 individuals from the Copenhagen General Population Study. Clin Chem 2011;57:482–489.

5) NICE clinical guideline CG181. Lipid modification: cardiovascular risk assessment and the modification of blood lipids for the primary and secondary prevention of Cardiovascular disease. Available from https://www.nice.org.uk/guidance/cg181/evidence/lipidmodification-update-full-guideline-243786637 (24 October 2015)

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