Cholesterol Screening Tests Explained
A comprehensive understanding of cardiovascular health involves more than just a simple cholesterol test. A lipid panel, or lipid profile, provides a more detailed and actionable assessment of heart disease risk.
A lipid panel measures multiple fats in the blood, including HDL cholesterol, LDL cholesterol, triglycerides, total cholesterol, and sometimes VLDL. This test offers a nuanced view of lipid-related risk factors for coronary heart disease (CHD).
HDL (high-density lipoprotein), often referred to as "good" cholesterol, helps remove LDL ("bad" cholesterol) from arteries, lowering the risk of heart disease. LDL (low-density lipoprotein), on the other hand, can build up in artery walls, increasing the risk. Triglycerides are a form of fat whose elevated levels independently raise cardiovascular risk. Total cholesterol sums these measures but does not discriminate between harmful and beneficial types. VLDL is related to triglycerides and is estimated from them; it also contributes to risk but is not often measured directly.
Because LDL is typically estimated using formulas that consider other lipid values, the lipid panel—and even extended lipid testing (like ApoB for particle number)—offers a richer understanding of cardiovascular risk than a simple total cholesterol measurement.
Tests that indicate subclinical atherosclerosis can be useful for people at increased risk of cardiovascular disease. Biomarkers of cardiovascular disease include homocysteine, fibrinogen, C-reactive protein, B-type natriuretic peptide, and D-dimer. Measuring certain biomarkers, such as C-reactive protein, could help doctors determine the level of therapeutic intensity for high cholesterol and high blood pressure.
It's important to note that factors such as age, sex, seasonal variations, recent changes in diet or weight, alcohol intake, exercise, family history, other illnesses, pregnancy, and certain medications can influence the accuracy of cholesterol tests. A family history of elevated lipids is significant because genetic forms of high cholesterol often do not respond fully to diet therapy.
In certain cases, the use of advanced lipid testing, measures of biomarkers, or tests for subclinical atherosclerosis can be useful but should be evaluated by an expert to avoid misinterpretation and unnecessary testing or treatment.
When admitted to the hospital for a major vascular event, such as a heart attack or stroke, cholesterol measurements should be taken immediately or within at least 24 hours. After such an event, LDL-cholesterol levels fall and stay low for weeks. Physicians should then wait at least eight weeks before performing cholesterol measurements.
Diet therapy is considered the cornerstone of cholesterol-controlling therapy, and drug therapy should be considered only when diet therapy has failed to lower blood cholesterol to an acceptable level. Even with diet therapy, periodic cholesterol testing should be performed to monitor progress and adjust treatment as needed.
Excessive alcohol intake raises triglyceride levels and HDL levels. To ensure consistent cholesterol test results, it is recommended to maintain a stable diet and weight for at least two weeks before the test. Some medications used to treat other medical problems can also affect cholesterol levels, including medications used to lower blood pressure, estrogen preparations, and anabolic steroids.
In addition to these biologic factors, situational factors must also be considered when cholesterol values are interpreted, including fasting, posture for the 30 minutes before the blood is drawn, recent surgery, and recent illnesses such as heart attack and infection.
For people with two or more risk factors and a Framingham 10-year risk scoring of 10 to 20 percent, the test could result in a change in treatment. The ankle-brachial blood pressure index (ABI) can diagnose peripheral arterial disease (PAD) and identify middle-aged men whose blood supply to the heart has been reduced due to narrowed arteries.
Before treatment is begun, your doctor will decide whether laboratory studies should be performed to rule out secondary causes of high blood cholesterol. This may include a blood or urine test to rule out pregnancy, a blood test to diagnose hypothyroidism or hyperthyroidism, a urine test to rule out nephrotic syndrome, a fasting blood sugar test to see if diabetes is present, and liver function tests to see if there is evidence of obstructive liver disease.
Cholesterol levels are higher in males over the age of 20 compared to females, and they increase in women after menopause. Seasonal variations have been shown to affect cholesterol values, with levels being higher in December compared to June. Carotid sonography can determine carotid intimal medial thickness (IMT), which measures the severity of atherosclerosis affecting the carotid arteries that supply the brain with blood.
Vigorous exercise just before a blood test can temporarily lower cholesterol and triglyceride values, but may also raise the level of a muscle enzyme called CPK. It is wise to take a day off from intense workouts just before the test. A recent study found that biomarkers only slightly improved the prediction of death and major cardiovascular events compared to traditional evaluation methods. Cholesterol values rise progressively in pregnancy and often take from several months to a year to return to pre-pregnancy levels.
Coronary calcium, a test that measures the amount of calcium in the coronary arteries, is not routinely recommended but can be useful in people who are more likely to have coronary heart disease. Even your posture before the blood test can affect the values obtained. A blood sample drawn after you've been sitting for 30 minutes will show a higher cholesterol level than a sample drawn when you're lying down.
In conclusion, a lipid panel's multiple measurements and ratios provide a nuanced and clinically actionable assessment of heart disease risk, whereas a basic cholesterol test (total cholesterol alone) lacks this detail and predictive power. It's essential to consider various factors when interpreting cholesterol test results and to work closely with healthcare professionals to manage cardiovascular risk effectively.
[1] Mayo Clinic. (2021). Cholesterol levels: Testing, normal ranges, and what they mean. [online] Available at: https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/cholesterol-testing/art-20045289
[2] National Heart, Lung, and Blood Institute. (2021). What is a lipid panel? [online] Available at: https://www.nhlbi.nih.gov/health-topics/lipid-panel
[3] American Heart Association. (2021). What is a lipid panel? [online] Available at: https://www.heart.org/en/health-topics/cholesterol/understanding-cholesterol/what-is-a-lipid-panel
[4] American Heart Association. (2021). Understanding your cholesterol test results. [online] Available at: https://www.heart.org/en/health-topics/cholesterol/understanding-cholesterol/understanding-your-cholesterol-test-results
- The lipid panel, a more comprehensive cholesterol test, not only includes total cholesterol but also measures HDL, LDL, triglycerides, and VLDL, offering a detailed view of lipid-related risk factors for cardiovascular health.
- In addition to conventional lipid-related factors, health and wellness professionals should consider various biomarkers, such as homocysteine, fibrinogen, C-reactive protein, B-type natriuretic peptide, and D-dimer, to assess cardiovascular disease risk.
- In the medical-condition context, genetic forms of high cholesterol may remain un responsive to diet therapy, necessitating further investigation and potential treatment with drugs.
