From the Guidelines
A fasted state is not always necessary for a lipid profile, as nonfasting samples can provide acceptably accurate measures for risk calculation, with modest differences in LDL-C levels between fasting and non-fasting samples 1.
Key Points
- Nonfasting lipid profiles are generally adequate to document baseline lipid levels prior to initiation of statin therapy, with the exception of individuals with triglyceride levels ≥400 mg/dL, where a repeat fasting lipid profile is recommended 1.
- Fasting lipid profiles are reasonable for initial evaluation in adults with a family history of premature ASCVD or genetic hyperlipidemia 1.
- Triglyceride measurement has the advantage of being a direct, precise, and accurate measurement of all triglycerides in plasma, but high triglycerides should be viewed as a marker of high levels of cholesterol in triglyceride-rich lipoproteins, rather than a cause of atherosclerosis itself 1.
- Remnant cholesterol, which can be estimated as total cholesterol minus LDL cholesterol minus HDL cholesterol, is a more accurate predictor of CVD risk than triglyceride levels alone, especially in individuals with hypertriglyceridemia 1.
Clinical Implications
- Nonfasting lipid profiles can be used to estimate ASCVD risk and document baseline LDL-C in most patients, reducing the burden of routine fasting lipid measures on patients and laboratories 1.
- Fasting lipid profiles should be used in specific cases, such as in individuals with triglyceride levels ≥400 mg/dL or in those with a family history of premature ASCVD or genetic hyperlipidemia, to provide a more accurate assessment of LDL-C and triglyceride levels 1.
From the Research
Significance of a Fasted State for a Lipid Profile
- The necessity of a fasting lipid profile has been debated in recent years, with some studies suggesting that it may not be necessary for determining cardiovascular risk 2, 3, 4, 5.
- Research has shown that lipid values in fasting and non-fasting lipid profiles have minimal differences, and non-fasting lipid profiles can be equally accurate in predicting cardiovascular risk 2, 3, 4.
- However, some studies suggest that fasting for lipid profile testing may still be preferred to reduce variability and increase consistency in patients' metabolic status 6.
- Certain patients, such as those with severe hypertriglyceridemias or high-risk patients being treated to low LDL-C levels, may still need fasting lipid panels performed for precise diagnosis and to standardize therapeutic monitoring 5.
Key Findings
- A study published in 2020 found that a non-fasting lipid profile is equally accurate in predicting cardiovascular risk, and that fasting is only necessary in select cases, such as non-fasting triglycerides > 8 mmol/l (708 mg/dl) 2.
- A 2012 study found that fasting times showed little association with lipid subclass levels in a community-based population, suggesting that fasting for routine lipid levels is largely unnecessary 3.
- A 2019 study found that non-fasting triglycerides are superior to fasting triglycerides in predicting cardiovascular risk, and that lipid-lowering trials using non-fasting blood samples found that reducing levels of non-fasting lipids reduced the risk of cardiovascular disease 4.
- A 2018 review found that non-fasting lipid assessment is reasonable in many clinical circumstances, given that ASCVD risk prediction is similar using fasting or non-fasting lipid values, and that LDL-C can be accurately estimated using modern methods 5.
Variability in Lipid Levels
- Studies have shown that lipid levels can vary slightly depending on fasting status, with non-fasting triglycerides approximately 20% higher on average compared to fasting levels 5.
- However, the magnitude of difference is subject to substantial inter-patient variability, and the clinical relevance of these differences is still debated 5.