New Gene Test For Diagnosis Of Heart Diseases
Angiography has been the predominant method to detect clogged arteries and diagnose heart diseases so far. It is carried out in cardiac catheterization labs of hospitals. However, it is pretty expensive and even risky as it exposes the internal organs of the body to radiation. Yet thousands of Americans have to get angiograms each year, most of which turn out to be negative, to detect if they are developing clogged arteries and are at risk of having heart attacks.
A new gene test for the diagnosis of heart diseases has the potential to reduce the number of these unnecessary angiograms. Through an easy to carry out blood test, it can find out whether one really needs an angiogram and then, those who need can go for it, while others may be spared the pain and money. It became available last year, and since then more than 6000 people have taken it.
However, the gene test is not perfect. It has many drawbacks which need to be addressed. It has given positive results for too many chest pain sufferers who really don’t have heart diseases, and negative for many who do. This is why several heart experts are still skeptical, saying they would wait for more results before they can use it.
Similar tests are being used now to determine the necessity of breast cancer treatments and organ transplants. With the discovery of more genes that affect the risk of heart disease, therefore, it can ultimately prove effective for heart ailments as well.
A journal of the American Heart Association is shortly going to publish the results of an extensive study to gather more information about these genes. The study was carried out by an international group of scientists.
“This may finally help in reducing unnecessary angiograms,” said Dr. Eric Topol of Scripps Health, La Jolla, CA., about the test.
Dr. Topol led a group of scientists who carried out a study of various aspects of the test, which is known as Corus CAD. The study was financially supported by CardioDx of Palo Alto, CA, the developer of the test. Although some researchers of CardioDx were part of the study, Dr. Topol was an independent researcher with no financial ties with the company. The results of the study were published in the Annals of Internal Medicine.
No doubt, chest pain is a serious symptom which may be indicative of a clogged artery that could cause a heart attack. As such, it can never be ignored. However, not all cases of chest pain are associated with clogged arteries. Many patients suffer from chronic chest pain which might be the result of other, less serious causes, like anxiety.
The gene test is intended for these patients. With a cost of US$1,195, it is a lot cheaper than angiography, and is being paid for by many insurance companies on a case-to-case basis. The results of the test take three days to arrive.
While most other gene tests predict the odds of developing heart disease some day, this test finds out whether the patient has it now. It is different from other gene tests as it does not look for particular genes or gene mutations; instead, it measures the activity level of the 23 key genes.
Compare these 23 genes with as many people sitting in a room, all talking at once in order to take some decision, and you listening to it. Can you find out the voices that matter most and guess the decision the group is likely to arrive at. Well, the test also acts the same way.
It was developed on the basis of gene information derived from 226 patients and analyzed further in 640 patients. Validation studies were conducted in 526 other patients. All of these had symptoms that would warrant angiography.
Angiography involves inserting a tube into a vein in the groin and injecting a dye so that clogs in the heart arteries are stained and show up in an X-ray. It is indeed a very reliable procedure, the gold standard in the diagnosis of heart disease. However, it costs upwards of $30,000 and exposes internal organs to the risk of X-rays, besides being inconvenient and painful.
To determine whether an angiogram is required, doctors take into account the patient’s age, sex and type of the chest pain he is suffering from. With the gene test, 16% more were recommended angiograms than had been recommended by doctors. All of them were diagnosed with heart disease when angiograms were taken later on. That means, out of 100 patients, 16 were correctly diagnosed for heart disease who would otherwise have been missed.
The test is a step forward in using genetic techniques to improve health care. However, as Donna Arnett, a genetic expert at the University of Alabama, wrote in her editorial, the results at this stage “do not provide compelling evidence” to go all out for it.
Dr. Harlan Krumholz, cardiologist and health outcomes researcher of the Yale University, agreed with her.
So, as of now, the test will most likely be used as a research tool. But with further improvements, it might help doctors in carrying out a better diagnosis and lead them to recommend fewer angiograms as preventive medicine, as asserted by Dr. Daniel Rader, director of preventive cardiology, University of Pennsylvania, and a spokesman for the American College of Cardiology.