Lp(a)

Lp(a) is not currently routinely ordered. It may be ordered along with other lipid tests to selectively screen for risk factors for coronary artery disease (CAD) and cerebral vascular disease. Lp(a) and several other emerging cardiac risk markers (such as Apo B, hs-CRP, Apo A, and homocysteine levels) are ordered on patients who have a strong family history of premature coronary artery disease.

Some doctors may also order these tests on patients with existing heart or vascular disease, especially those who have normal or only mildly elevated lipids. Since about 50% of the people who have heart attacks have normal cholesterol levels, doctors are starting to look at other factors that may have an influence on heart disease. It is thought that elevated Lp(a) levels can exacerbate other heart and vascular disease processes.

Lp(a) may be ordered, along with other lipid tests, when you have a family history of premature coronary artery disease and when your doctor suspects a familial hypercholesterolemia. He may also order an Lp(a) level when you have had a stroke or heart attack but have normal or only mildly elevated lipids.

In rare cases, an Lp(a) level may be ordered on a post menopausal woman to see if elevations in Lp(a) (tied to decreasing estrogen levels) have significantly increased her risk of developing CAD.

Lp(a) levels are genetically determined and remain relatively constant over an individual's lifetime. They are not affected by lifestyle changes or by most drugs.

High Lp(a) levels may increase a person's risk for developing coronary artery disease and cerebral vascular disease and can occur in patients with a normal lipid profile. Elevated levels of Lp(a) are thought to work independently, to add to any underlying heart or vascular disease processes. Other conditions that may cause elevated levels of Lp(a) include:

• Chronic renal failure
• Estrogen depletion
• Familial hypercholesterolemia - an inherited disorder involving high levels of blood cholesterol
• Severe hypothyroidism
• Uncontrolled diabetes
• Nephrotic syndrome

Low levels of Lp(a) do not appear to cause problems.

Lp(a) levels are not routinely ordered tests. A National Cholesterol Education Program (NCEP) guideline, the “Adult Treatment Panel III” (pg. II-21, available in PDF) acknowledged the possible usefulness of Lp(a) and other emerging cardiac risk tests like Lp(a), but it did not recommend them for widespread screening. The National Academy of Clinical Biochemistry (NACB) guidelines for emerging biomarkers of cardiovascular disease and stroke also recommend testing for individuals with a strong family history of premature risk of CVD or those with intermediate cardiovascular risk but not for general screening.

This is partially due to the fact that Lp(a) levels are genetically determined and difficult to change. Niacin and estrogen (for postmenopausal women) have been shown to lower Lp(a) levels a small amount, but their effect appears to be short term, and it is not known if lowering Lp(a) levels actually lowers risk. Experts are currently not recommending drug treatments for elevated Lp(a) levels, but some are suggesting that patients with elevated Lp(a) levels should be especially vigilant about lowering their low-density lipoprotein (LDL – the “bad” cholesterol) levels, which may help lower their overall risk.

In general, lipids should not be measured during a fever or major infection, within four weeks of an acute myocardial infarction (heart attack), a stroke, or major surgery, right after excessive alcohol intake, with severely uncontrolled diabetes, when a woman is pregnant, or during rapid weight loss.

Typically, Lp(a) levels are only tested once because they are usually fairly constant. Occasionally, your doctor may order a second Lp(a) to confirm the initial level or to see if your risk has increased significantly after menopause or to monitor the effects of treatment.