Tuesday, February 12, 2013

Genetic Screening Test for Familial High Cholesterol

Cholesterol is a waxy, fatty substance found only in animal tissues. Good cholesterol helps to eliminate bad cholesterol. There are two types of cholesterol: good cholesterol (also known as HDL which stands for high-density lipoprotein) and bad cholesterol (also known as LDL which stands for low-density lipoprotein).

LDL is called bad cholesterol because it can cause cholesterol to build up, which can lead to blockage of the arteries and heart disease. Arteries are blood vessels that pump blood away from the heart.

Cholesterol levels are easily detected through a routine blood test known as a lipid panel. When the doctor believes cholesterol is too high, lifestyle changes (e.g., increased exercise, diet changes) and medications may be prescribed.

While high cholesterol can be caused by a poor diet and not enough exercise, genetics can also play a role. In other words, some people have what is known as familial hypercholesterolemia, which is a fancy way of saying that the person has inherited very high levels of bad cholesterol from one or both parents, which leads to heart disease.

Unless someone goes for testing, the condition may not be detected because it usually does not cause symptoms. However, it can cause the sign of yellowish patches on the body due to cholesterol deposits. The condition is caused by mutations of genes. Genes are tiny structures that contain coded instructions for how certain bodily characteristics should develop.

To diagnose the condition early, some scientists have suggested using genetic screening methods. However, some have expressed concern that this can lead to an unacceptably high level of false positives, in which people are told they have the condition when they do not. One type of genetic testing is analyzes for genetic mutations that cause high cholesterol and is known as the High-Resolution Melting (HRM) method.

In the most recent issue of the Annals of Human Genetics, the HLRM method was used on eight unrelated people (7 females and 1 male) from Croatia known to have familial hypercholesterolemia. The test was positive in 7 cases (88%) in which the mutation causing the problem was found. The researchers concluded that the HLRM method is sensitive for detecting familial hypercholesterolemia, which can lead to earlier treatment and detection in other family members, which in turn, can prevent premature heart disease. One problem with the study is however is that no controls (people without the condition) were tested so the false positive rate is unknown. The study also has limited generalizability as it was mostly done with Croatian women.

Suggested reading: Cholesterol Down: Ten Simple Steps to Lower Your Cholesterol in Four Weeks--Without Prescription Drugs
Reference: Pećin I, Whittall R, Futema M, Sertić J, Reiner Z, Leigh SE, Humphries SE. (2013). Mutation detection in Croatian patients with familial hypercholesterolemia. Ann Hum Genet. 77(1):22-30.

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