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Is Fasting Required for Lipid Profile?

Current guidelines state that patients need to fast for 12-14 hours before examining the lipid profile. Not a few patients feel uncomfortable with fasting for a long time. However, several studies currently state that examining lipid profiles without fasting does not give many different results.

Is Fasting Required for Lipid Profile?
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Theories of the Fasting Effects on Lipid Profile

Dyslipidemia, especially hypercholesterolemia and hypertriglyceridemia, has a strong correlation with the risk of cardiovascular disease. Standard measurements for lipid profiles are total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides (TG).

In many laboratories, LDL is calculated based on the Friedewald formula (LDL = TC - HDL-TG / 5). This calculation is based on several assumptions that most cholesterol is transported by LDL, HDL, and very-low-density lipoprotein (VLDL) in fasting plasma conditions. Most triglycerides are associated with VLDL in the fasting state, and the standard ratio of triglycerides and cholesterol in VLDL is 5. However, this assumption is not entirely correct.

LDL and triglycerides measurement needs to be done in patients undergoing overnight fasting without any nutritional intake, except mineral water and drug because triglycerides (mostly in the form of chylomicrons) will tend to be high a few hours after eating. 

If the patient does not fast before, the triglyceride levels will be high, and the ratio of triglycerides and cholesterol will change from the standard ratio and make the Friedewald formula invalid. This is thought to cause overestimation of LDL results. 

Clinical Evidence of the association between Fasting and Lipid Profiles

Fasting protocols before conducting lipid profile laboratory tests have become recommendations and are carried out routinely in health services. However, several studies now find that the results of lipid profile examination without fasting are not significantly different and may even be superior compared to examinations that preceded fasting.

A cross-sectional community-based study that examined the relationship between fasting time and lipid levels showed a small association between fasting time and subclass lipid levels. This study examined fasting time from 1 hour to 16 hours and measured the average level of cholesterol subclass. The mean difference between fasting and non-fasting groups was> 2% for HDL and total cholesterol,> 10% for LDL, and> 20% for triglycerides. This study assessed one of the reasons non-fasting in lipid profiles tests that it makes patients uncomfortable and ultimately does not carry out routine screening because the examination is usually performed in the morning.

Reports that total cholesterol and HDL show relatively stable results in fasting time have major clinical implications because both tests are used as a predictor of cardiovascular risk, the Framingham risk score.

However, in some conditions, fasting is still needed in the examination of lipid profiles. Fasting is recommended to monitor the initial therapeutic response with statins. Also, if the focus of therapy is decreasing triglyceride levels, fasting should be done because food can influence triglyceride levels.

A cohort study conducted by Cartier et al. Compared the lipid profile of fasting and non-fasting patients. This study also obtained the same results, namely lipid parameters at postprandial only gave minimal changes in total cholesterol and HDL. The average difference between fasting and not on total cholesterol was 1.7%, HDL 0.8%, triglycerides 17%, and LDL 6.6%.

This study recommended examining triglycerides should be checked after fasting to obtain valid results. This study has limitations because several confounding factors can interfere with the examination results such as medication, physical activity, alcohol, and type of food.

In 2016, a consensus was published regarding the fasting protocol before examining the lipid profile. This consensus recommended measuring lipid profiles without fasting first. Measurements preceded by fasting may be considered if non-fasting triglycerides> 440 mg/dL.

In measuring lipid profiles that were not preceded by fasting, the recommended abnormal threshold values ​​were adalah175 mg/dL for triglycerides, 90190 mg/dL for total cholesterol, ≥115 mg/dL for LDL, and ≤40 mg/dL for HDL.

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3. Sepulveda J. Challenges in routine clinical chemistry testing: lipid profile. Science Direct. 2013. [cited 2018 December 4]. Available from: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/lipid-profile
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