Lipoprotein(a) [Lp(a)]

What is lipoprotein(a) [Lp(a)]?

Lipoprotein(a) is a cholesterol-carrying lipoprotein that is structurally similar to the LDL particle. It differs from LDL in that it carries apolipoprotein(a), an additional protein bound to the apolipoprotein B on its surface. This structure can increase the particle's tendency to build up in the artery wall and its interaction with clotting processes. A high Lp(a) level is regarded as a risk factor for cardiovascular disease and for narrowing of the aortic valve that is independent of other risk factors.

The Lp(a) level is largely genetically determined and depends on the genes inherited from the mother and the father. Lifestyle changes such as diet, exercise and weight loss often have only a limited effect on Lp(a). Because the level stays largely stable in adulthood, many guidelines recommend measuring it at least once in adulthood; the doctor decides whether it needs to be repeated. Because it is not shown separately in the standard cholesterol test, it has to be ordered as a separate test.

When is the Lp(a) test ordered?

The Lp(a) test is ordered to assess cardiovascular risk more comprehensively. Doctors may add this test to the assessment especially in people who have unexplained vascular disease even though their cholesterol values are under control, or in people with a family history of events such as heart attack or stroke at a young age. Because of its inherited nature, measurement may also be recommended for the first-degree relatives of people found to have high Lp(a).

• A family history of cardiovascular disease at a young age
• A heart attack, stroke or vascular blockage at a young age
• Suspected or diagnosed familial high cholesterol
• LDL cholesterol not falling as much as expected despite treatment
• Narrowing of the aortic valve
• A relative found to have high Lp(a)

The Lp(a) test is a screening or risk assessment tool and does not make a diagnosis on its own. Your doctor often orders this test together with total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides and, if needed, Apo B. The result becomes meaningful when it is assessed together with the person's age, sex, blood pressure, blood sugar status, smoking and family history.

How do you prepare for the Lp(a) test?

No fasting is needed for Lp(a) measurement; the level is not significantly affected by meals, and the sample can be given at any time of day. However, if Lp(a) is ordered together with a lipid profile that also includes triglycerides and LDL cholesterol, your doctor may ask you to fast before the blood draw. If you have received such an instruction, it is best to plan your appointment accordingly.

Lp(a) can rise temporarily during acute inflammatory conditions in the body; for this reason, if the measurement is to be done during a feverish illness or shortly after surgery, it is helpful to let your doctor know. It is also important to mention the medications and hormone therapies you use. The blood sample is collected by a nurse at your home or workplace and analyzed at an accredited laboratory.

What does an Lp(a) result mean?

A high Lp(a) level is regarded as an inherited trait that can increase the predisposition to cardiovascular disease; on its own, it does not mean disease or a definite prediction of the future. In this case, your doctor may generally recommend focusing more on the other risk factors that can be changed, namely LDL cholesterol, blood pressure, blood sugar status, smoking and weight. Kidney disease, an underactive thyroid gland and menopause can also raise Lp(a) levels.

An Lp(a) result in the normal range suggests that this particle does not pose a significant additional risk for the person. Results may be reported in different units by different laboratories, and depending on the measurement method used, values may not be directly comparable; for this reason, the laboratory's own reference range is given in the result report. Your Lp(a) result should be interpreted by your doctor together with other lipid tests, your family history and your general health.