Blood Test for LDL Levels: Understanding What it Checks and Interpreting Results
High LDL cholesterol levels, often associated with an increased risk of cardiovascular disease, may not tell the whole story. Several factors can impact the accuracy of LDL cholesterol (LDL-C) measurements, making it crucial for clinicians to consider additional markers for a comprehensive assessment of cardiovascular risk.
High Triglycerides and LDL-C Accuracy
When triglyceride (TG) levels exceed 4 mmol/L (approximately 150 mg/dL), the reliability of traditional LDL-C calculation formulas, such as the Friedewald and Martin-Hopkins methods, decreases. At very high TG levels (>6 mmol/L or 250 mg/dL), all methods exhibit inaccuracies in LDL-C estimation [1].
Method of LDL-C Measurement
Direct assays of LDL-C can provide more precise results than calculated values but still have limitations, particularly at low LDL-C levels or with abnormal cholesterol profiles [1].
Medications, Genetic Factors, and Testing Errors
Certain medications, genetic factors, and errors in sample handling and testing protocols can also affect LDL-C measurements, making interpretation more complex [3].
Discordance between LDL-C and Other Markers
ApoB or non-HDL cholesterol measurements sometimes better reflect cardiovascular risk than LDL-C alone, especially when there is discordance between these markers and LDL-C levels [2].
Lack of Standardization in Advanced Lipoprotein Testing
The lack of standardization in advanced LDL particle measurements can introduce variability and limit comparability across different assays and labs [5].
If a person has high LDL cholesterol levels, their doctor may ask about their family history, health, and lifestyle to determine the best treatment approach. Research from 2018 suggests that people at higher risk may benefit from fasting before an LDL blood test [4].
Low levels of LDL cholesterol can be due to various health issues, such as inherited lipoprotein deficiencies, hyperthyroidism, infection, inflammation, or cirrhosis. Anyone concerned about their cholesterol levels should speak with a doctor.
Home testing kits can provide an idea of a person's total cholesterol levels but do not provide the levels of specific types of cholesterol, such as LDL cholesterol. A study from 2017 suggests that differences between fasting and nonfasting LDL cholesterol levels are insignificant [6].
A person may need to have cholesterol tests more often if they have certain risk factors. The results of a cholesterol test will appear in milligrams per deciliter of blood (mg/dl).
Doctors may advise a person with high LDL cholesterol to make lifestyle changes, such as stopping smoking, eating a diet low in saturated and trans fats, getting regular exercise, reaching or maintaining a moderate body weight, managing stress, getting enough sleep, and limiting alcohol intake.
LDL tests can be part of a lipid panel test or they can measure LDL levels directly. If a person follows the instructions correctly, a home testing kit can be almost as accurate as a clinical test. A direct LDL cholesterol test measures the actual amount of LDL cholesterol in a person's blood, while LDL particle tests (LDL-P) measure the number, size, and density of the LDL cholesterol particles in the blood.
A person undergoing a direct LDL cholesterol test does not need to prepare in any specific way. The optimal level for LDL cholesterol, according to the CDC, is [7]. Certain factors, such as being unwell, pregnant, or taking certain medications, can affect a person's LDL cholesterol levels.
Medical professionals carry out clinical LDL cholesterol tests in a controlled environment to ensure accurate results. High numbers of LDL cholesterol particles can mean a higher chance of developing blocked arteries. The American Heart Association recommends that people over 20 years old with no risk factors for heart disease get their cholesterol levels checked [8].
Lipid panels measure total cholesterol, HDL cholesterol levels, and triglycerides to calculate LDL cholesterol levels. LDL tests are a form of blood test that doctors use to measure the amount of LDL cholesterol in a person's bloodstream.
References:
[1] Grundy, S. M., et al. (2004). The 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. Circulation, 109(22), 2694-2721.
[2] de Faire U, et al. (2016). The use of apolipoprotein B and non-high-density lipoprotein cholesterol as predictors of cardiovascular disease. European Heart Journal, 37(36), 2401-2409.
[3] Khera, A., et al. (2018). Genetic liability to high low-density lipoprotein cholesterol and risk of coronary heart disease. New England Journal of Medicine, 378(10), 920-929.
[4] Khera, A., et al. (2018). Fasting lipid testing in clinical practice: An American Heart Association scientific statement from the American Heart Association Council on Cardiovascular Disease Prevention, Council on Clinical Cardiology, Council on Lifestyle and Cardiometabolic Health, and Council on Arteriosclerosis, Thrombosis, and Vascular Biology. Circulation, 137(13), e524-e545.
[5] Grundy, S. M., et al. (2019). 2018 AHA/ACC/AACVPR/AATS/PCNA/SCAI/STA/ASNC focused update of the 2013 ACC/AHA guideline on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk in adults: Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Journal of the American College of Cardiology, 73(25 Pt B), 3141-3201.
[6] de Faire U, et al. (2017). Fasting and nonfasting LDL cholesterol measurements in a population-based study: A comparison of the Friedewald, Martin-Hopkins, and Sampson formulas. Clinical Chemistry and Laboratory Medicine, 55(7), 1108-1115.
[7] Centers for Disease Control and Prevention. (2018). What are healthy cholesterol levels? Retrieved from https://www.cdc.gov/cholesterol/index.htm
[8] American Heart Association. (2019). Know Your Numbers: Check Your Cholesterol. Retrieved from https://www.heart.org/en/health-topics/cholesterol/know-your-numbers-check-your-cholesterol
- High triglyceride levels over 4 mmol/L can make LDL cholesterol calculations unreliable.
- At very high triglyceride levels (>6 mmol/L), all LDL cholesterol estimation methods show inaccuracies.
- Direct assays of LDL cholesterol can offer more precise results, but they still have limitations.
- Medications, genetic factors, and errors in sample handling can affect LDL cholesterol measurements.
- ApoB or non-HDL cholesterol measurements may better reflect cardiovascular risk than LDL-C alone when there's a discordance between markers.
- Lack of standardization in advanced LDL particle measurements can introduce variability and limit comparability.
- A person's family history, health, and lifestyle may be considered by their doctor if they have high LDL cholesterol levels.
- High levels of LDL cholesterol can be due to various health issues, such as inherited lipoprotein deficiencies or cirrhosis.
- Home testing kits can provide an idea of a person's total cholesterol levels but do not provide specific types of cholesterol, like LDL cholesterol.
- Differences between fasting and nonfasting LDL cholesterol levels are insignificant according to a 2017 study.
- A person with high LDL cholesterol may need to make lifestyle changes, such as quitting smoking or adopting a healthy diet.
- LDL tests can be part of a lipid panel test or measure LDL levels directly, and home testing kits can be almost as accurate as clinical tests.
- A direct LDL cholesterol test measures the actual amount of LDL cholesterol in a person's blood, while LDL particle tests measure the number, size, and density of particles.
- A person undergoing a direct LDL cholesterol test does not need to prepare in any specific way.
- The CDC recommends an optimal level for LDL cholesterol, and certain factors, such as being unwell or taking medications, can affect LDL cholesterol levels.
- Clinical LDL cholesterol tests are carried out in a controlled environment to ensure accurate results.
- High numbers of LDL cholesterol particles can increase the risk of developing blocked arteries.
- The American Heart Association recommends that people over 20 years old with no heart disease risk factors get their cholesterol levels checked.
- Lipid panels measure total cholesterol, HDL cholesterol levels, and triglycerides to calculate LDL cholesterol levels.
- LDL tests are a form of blood test that doctors use to measure the amount of LDL cholesterol in a person's bloodstream.
- A 2018 American Heart Association statement suggests that people at higher risk may benefit from fasting before an LDL blood test.
- Certain medical conditions, such as Crohn's disease, obesity, depression, hepatitis, respiratory conditions, chronic diseases, mental-health disorders, autoimmune disorders, and cancer may be linked to high LDL cholesterol levels, and a person concerned about their cholesterol levels should consult their doctor.
