Direct LDL Cholesterol

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

To determine your chances of developing cardiovascular disease or to detect genetic cholesterol conditions.

When this test is required

LDL-C, as part of a lipid profile, is commonly tested by your GP when you reach the age of 40, as part of a routine cardiovascular health check.It may be checked at other times if you are thought to be at increased risk of cardiovascular disease for another reason.Finally, it will likely be checked at regular intervals if you have been prescribed treatments to help lower your LDL-C, such as statins.

What the Test Detects

Cholesterol is carried in the blood by proteins called “lipoproteins”. There are a number of different types of lipoproteins, which are named after how dense they are. LDL stands for ‘low-density lipoprotein’, and any cholesterol carried by LDL is known as LDL cholesterol, or LDL-C. LDL is considered to be undesirable because it deposits excess cholesterol in the walls of blood vessels and contributes to atherosclerosis, also…Cholesterol is carried in the blood by proteins called “lipoproteins”. There are a number of different types of lipoproteins, which are named after how dense they are. LDL stands for ‘low-density lipoprotein’, and any cholesterol carried by LDL is known as LDL cholesterol, or LDL-C. LDL is considered to be undesirable because it deposits excess cholesterol in the walls of blood vessels and contributes to atherosclerosis, also known as ‘hardening of the arteries’ or ‘furring up of the arteries’, and ultimately cardiovascular disease, such as heart disease and strokes. Hence LDL-C is often termed ‘bad’ cholesterol. LDL-C is usually tested as part of a lipid profile. This includes the total cholesterol as well as a “breakdown” of how much of that cholesterol is carried on LDL (ie LDL-C), and how much is carried on ‘high density lipoprotein’ (ie HDL cholesterol). Triglycerides are also measured as part of the lipid profile. In fact, LDL-C is usually not measured directly, but calculated using an equation (see below, Common Questions) which uses the other components of the lipid profile. Occasionally LDL-C can be measured directly. See MoreSee Less

Preparation for the Test

A test for LDL-C typically requires a 12-hour fast, with only water permitted during this time. Strictly speaking, if LDL-C is being measured directly, rather than calculated using an equation (see below, Common Questions), fasting is not necessary but most labs only calculate it. Also it has been shown that as long as triglycerides are not significantly raised non-fasting results can be used to calculate the LDL-C therefore most of the time fasting is not required. Follow any instructions you are given.

Sample Requirements

The test for LDL-C uses a blood sample. Most often, the blood sample is collected by venepuncture (using a needle to collect blood from a vein in the arm). Occasionally a fingerprick test can be used, although this is not commonly available in GP practices or hospitals in the UK.

Additional Notes

There is condition which runs in families called “familial hypercholesterolaemia” in which LDL-C is very high – usually over 4.9 mmol/L in adults. Some people, though not all, who have an LDL-C this high, have familial hypercholesterolaemia. This is an inherited condition which is important to pick up, as if it isn’t treated there is a high risk of heart disease at a young age. Furthermore, as it is inherited, other family members might be affected. Anyone suspected of having familial hypercholesterolaemia should be referred to a specialist lipid clinic.LDL-C should be measured when a person is healthy. LDL-C is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). You should wait at least six weeks after any illness to have LDL-C measured.In women, cholesterol is high during pregnancy. Women should wait at least six weeks after the baby is born to have LDL-C measured.

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