Direct LDL Cholesterol
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
Direct LDL cholesterol test — This test measures the amount of low-density lipoprotein (LDL) cholesterol in a blood sample, directly quantifying the level of “bad” cholesterol in the bloodstream. It is used to assess cardiovascular risk and monitor treatment for conditions such as high cholesterol and heart disease.
Why get tested?
To help determine your risk of developing heart disease and to monitor lipid-lowering lifestyle changes and drug therapies; to accurately determine your low-density lipoprotein cholesterol (LDL‑C) concentration when you have raised triglyceride concentrations
When to get tested?
As a follow-up to a lipid profile if your triglycerides are significantly elevated; at regular intervals to monitor efforts to lower LDL concentrations.
Sample required?
A blood sample taken from a vein in your arm.
Test preparation needed?
No test preparation is needed. Your doctor might recommend that you fast (water only) for 14 hours prior to the test so that other related substances can be measured in the same sample.
Common questions
Measurement of low density lipoprotein cholesterol (LDL‑C) is helpful in assessing a patient’s risk of heart disease and in monitoring the response to lipid lowering therapy. A standard lipid profile consists of total cholesterol, high-density lipoprotein cholesterol (HDL‑C), and triglycerides. By applying a formula, the amount of cholesterol present in low-density lipoprotein can be determined, and this calculated value is typically reported alongside the other values. When triglycerides are high, the formula can no longer be used and the only way to accurately determine LDL‑C is to measure it directly.
High triglycerides may be due to a metabolic disorder affecting lipids. However, anyone may have high triglycerides concentrations in their blood after eating. In either situation, the direct LDL‑C test can determine the amount of LDL in a patient’s blood.
LDL‑C may not be included in all standard lipid profiles, as non-HDL cholesterol is increasingly being used to estimate future cardiovascular risk in many situations rather than LDL‑C. Non-HDL cholesterol accounts for other forms of “bad” cholesterol in addition to LDL‑C. In some cases both LDL‑C and non-HDL cholesterol are reported.
Direct LDL‑C may be requested when calculation of LDL cholesterol will not be accurate because the patient’s triglycerides are significantly elevated.
Elevated concentrations of LDL, as measured with the direct LDL‑C test, indicate a greater risk of developing heart disease. Concentrations of LDL‑C decrease in response to lipid-lowering lifestyle changes and/or drug therapies indicating a decreased risk of heart disease.
Low concentrations of LDL are not generally a concern and are not monitored. They may be seen in patients with an inherited lipoprotein deficiency and in patients with hyperthyroidism, infection, and inflammation.
Direct LDL‑C, like calculated LDL‑C, should be measured when you are well and “metabolically stable.” Illness, surgery, trauma, a heart attack, sudden weight loss or gain, and pregnancy can all temporarily affect the LDL concentration.
Calculated LDL‑C is almost as accurate as direct LDL‑C when triglyceride concentrations are normal. It can be done at no additional cost when a standard lipid profile is performed whereas the use of direct testing increases the cost.
No, LDL and other lipoprotein molecules vary in size and density. Patients with a larger percentage of small dense LDL molecules are believed to be at greater risk for developing atherosclerosis than those with a higher percentage of large LDL. Different sizes of lipoprotein molecules can be separated by density (through ultra-centrifugation), by size and electrical charge (through electrophoresis) and by other techniques. The clinical usefulness of these tests is however, still to be proven.