Reviewed and updated by Myrna Buiser Schnur, MSN, RN: April 30, 2024
When we think of heart health, we often think about diet and how we can lower our cholesterol. For our patients, assessing their lipid profile helps determine their risk for cardiovascular disease. The lipid profile also helps to identify patients at risk for familial hypercholesterolemia, identify potential causes of pancreatitis, manage patients with atherosclerotic cardiovascular disease (ASCVD), and evaluate the effectiveness or compliance with lipid-lowering therapy and lifestyle modification (Sandeep, 2024). Let’s take a closer look at the lipid components in our blood.
There are five major lipoproteins in our blood: chylomicrons, very low-density lipoprotein (VLDL); intermediate-density lipoprotein (IDL); low-density lipoprotein (LDL), and high-density lipoprotein (HDL) (Vijan, 2024). Each carries varying amounts of cholesterol and triglycerides. LDL carries most of the cholesterol and VLDL act as the major carrier of triglycerides. A typical blood lipid profile measures total cholesterol, HDL cholesterol and triglycerides. The LDL cholesterol is then estimated from these values.
The target range for cholesterol levels are (Centers for Disease Control and Prevention [CDC], 2020):
| Lipid Profile |
Normal Range |
| Total cholesterol |
Less than 200 mg/dL |
| LDL (“bad”) cholesterol [LDL-C] |
Less than 100 mg/dL |
| HDL (“good”) cholesterol [HDL-C] |
Greater than or equal to 60 mg/dL |
| Triglycerides [TG] |
Less than 150 mg/dL |
Fasting versus Non-fasting Testing
Fasting (8 to 12 hours without food) is not typically required for lipid testing except for first time lipid measurements and for patients being followed for known hypertriglyceridemia. A fasting lipid profile may also be needed for the following:
- If screening cholesterol is greater than 250 mg/dL
- If screening HDL cholesterol is lower than 40 mg/dL
- Family history of genetic hyperlipidemia
- Assessing patients for hypertriglyceridemia
- Patients who are overweight
- Patients with diabetes
- Patients with significant alcohol intake
- Patients on medications, such as steroids, that increase triglyceride values
If a non-fasting plasma triglyceride returns greater than 400 mg/dL, a fasting lipid profile should be drawn.
Lipid Profile Components (Rosenson, 2022)
LDL-C
LDL-C, or “bad” cholesterol, at high levels, can build up in the arteries and increase a person’s risk for heart attack, stroke, and peripheral artery disease (American Heart Association [AHA], 2017). LDL-C is the primary lipid measure for cardiovascular disease risk assessment and helps guide treatment strategies. For patients undergoing lipid-lowering modifications, it should be monitored every six weeks after the initiation of therapy until the LDL-C target level is reached. Measurements can then be checked every 6 to 12 months.
LDL-C is often calculated using the Friedewald equation, Martin/Hopkins method, the Sampson/NIH method, or by direct measurement if total triglyceride level is greater than 400 mg/dL.
Friedewald equation: LDL cholesterol = Total cholesterol – VLDL cholesterol – HDL cholesterol
There are several drawbacks to the Friedewald equation. It is an estimation as the VLDL cannot be measured directly. VLDL is calculated by dividing the total triglycerides by 5. All values must be obtained from a patient in the fasting state and the formula cannot be used if a patient’s total triglyceride level is greater than 400 mg/dL.
The
Martin/Hopkin equation has been cited as more accurate than the Friedewald equation in patients with an LDL-C level less than 70 mg/dL and triglyceride level greater than 150 mg/dL (Ferraro et al., 2019). This equation utilizes adaptable ratios based on a patient’s individualized non-HDL-C and triglyceride values. Another advantage of this equation is that it does not require the patient to fast prior to testing.
The
Sampson/NIH method can be used in patients with plasma triglyceride levels up to 800 mg/dL. The most accurate measure of LDL-C utilizes
ultracentrifugation; however this process is complex and costly.
Direct measurement using LDL-C assays or chemical-based methods are not reliable or standardized and may be less accurate than the Friedewald equation (Ferraro et al., 2019).
Non-HDL-C
Measuring
Non-HDL-C provides another method to estimate risk from atherogenic lipoproteins, those that tend to form fatty plaques in the arteries. It is calculated by subtracting HDL-C from total cholesterol and includes all cholesterol present in lipoprotein particles that are considered atherogenic, including LDL-C, lipoprotein (a), IDL, and VLDL. This value is useful in people with low or normal LDL-C, low HDL-C, and elevated triglycerides (200 mg/dL or greater). Non-HDL-C is also a sensitive screening test of dyslipidemia in children (de Ferranti & Newburger, 2020). However, this lab test is not routinely measured.
HDL-C
HDL-C is considered the “good” cholesterol because it carries LDL cholesterol away from the arteries to the liver to be broken down and eliminated from the body (AHA, 2017). Only about a third to a fourth of the total LDL is carried by HDL. A healthy HDL cholesterol level may help decrease the risk of heart attack and stroke while low levels of HDL increase these risks (AHA, 2017), however a causal relationship has not been established. HDL-C is measured directly, and blood samples may be drawn in the fasting or non-fasting state.
Triglycerides
A high
triglyceride level combined with a high LDL or low HDL may cause fat build up within the arteries, increasing the risk of heart attack and stroke (AHA, 2017). Triglyceride levels help identify patients with other metabolic disorders such as diabetes, steatosis, or non-alcoholic fatty liver disease. Monitoring triglyceride levels will help practitioners identify the underlying cause of acute pancreatitis, monitor treatment of hypertriglyceridemia, and screen family members for familial hypertriglyceridemia. Triglycerides should be measured with patients in the fasting state when possible.
Screening (Sandeep, 2024)
Children with one or more risk factors for premature cardiovascular disease (CVD) should undergo selective screening (de Ferranti & Newburger, 2020). Children without CVD risk factors should be screened for dyslipidemia twice: between ages 9 and 11 years and again between 17 and 21 years (de Ferranti & Newburger, 2020). Young adults who were not screened as children, should have a lipid profile drawn when they begin seeing an adult primary care practitioner to screen for familial hyperlipidemia and to assess cardiovascular risk (Sandeep, 2024). If the results are normal, the timing and frequency of future screening should be determined by the patient’s risk for cardiovascular disease and possible interventions that can enhance patient outcomes. For lower risk adults, Sandeep (2024) suggests follow-up lipid screening begin at age 35 in males and 45 in females, then repeat every five years. More frequent screening is recommended for patients with a family history of premature ASCVD or when multiple risk factors are present (i.e., repeat screening every three years) beginning at the age of 30 to 35 in males and 25 to 30 in females. Specific lipid-related, “risk-enhancing” clinical factors in borderline and intermediate ASCVD risk adults include:
- LDL-C greater than or equal to 160 mg/dL or non-HDL-C greater than or equal to 190 mg/L
- Fasting triglycerides greater than or equal to 175 mg/dL
- Lp(a) greater than or equal to 50 mg/dL
- Apolipoprotein B greater than 130 mg/dL
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