February 4, 2011 – More heart disease tests do not necessarily add up to a better diagnosis. According to a new practice guideline, a basic risk assessment that accounts for such factors as cholesterol level, blood pressure, age, sex, family history, smoking and diabetes is still the strongest tool a doctor can use in predicting the likelihood of heart disease. Beyond that, most tests that claim to predict heart disease risk are helpful only in selected cases.
Developed by the American College of Cardiology and the American Heart Association, the new guideline appears in the Dec. 14/21 issue of the Journal of the American College of Cardiology and the Dec. 21, 2010, issue of Circulation: Journal of the American Heart Association. It outlines which diagnostic tests are most useful in assessing cardiovascular risk in people who have no obvious signs of heart disease, and which tests do little to clarify the health picture.
After reviewing more than 400 scientific studies, the expert panel determined that only a global cardiovascular risk score and family history were essential for everyone, starting at age 20.
“There’s strong evidence that the basic risk assessment we’ve been advocating for years has a very, very strong ability to predict risk,” said Philip Greenland, M.D., a professor of medicine and preventive medicine at Northwestern University Feinberg School of Medicine in Chicago. “When new tests compete for attention we have to ask, ‘Do they add any new information?’”
Beyond that, the expert panel weighed whether new diagnostic information would change a physician’s treatment plan or a patient’s health habits, and whether that change would be powerful enough to improve health outcomes. As a result, many tests were found useful only in intermediate-risk patients, or those with a 10 to 20 percent risk of developing heart disease within 10 years. In low-risk patients, additional diagnostic tests seldom add useful predictive information, while in high-risk patients, the global risk score and family history make it obvious what the physician should do next.
Even tests such as C-reactive protein and coronary calcium scoring received nuanced and limited recommendations that reflect the data currently available from clinical studies.
“These guidelines are based on scientific evidence,” Greenland said. “Some people say that if you improve risk prediction you can assume you’ll improve patient outcomes, but it’s not so clear. All that prediction does is give the physician different information and the patient a different message. But those two things have to be potent enough to change what happens next. If you’re going to come out with a recommendation that a test should be done for everybody, it’s important to be confident of better patient outcomes.”
It includes the following recommendations for cardiovascular risk assessment in people without symptoms of heart disease:
Tests that should be performed in all adults for cardiovascular risk assessment
• Global risk scoring, taking into account such factors as cholesterol level, blood pressure, age, sex, diabetes and smoking
• Family history
Tests that are reasonable or may be considered in appropriate adults for cardiovascular risk assessment
• C-reactive protein, in intermediate-risk men age 50 and younger and women age 60 and younger, for cardiac risk assessment, plus a selected group of older people, for determining whether statin therapy is warranted
• Coronary artery calcium scoring, in people with diabetes age 40 and older, in intermediate-risk people and, possibly, those at low-to-intermediate risk
• Resting electrocardiogram (ECG), especially in people with high blood pressure or diabetes
• Ankle-brachial index, in intermediate-risk people, to test for atherosclerosis in the arteries of the legs
• Carotid intima-media thickness, in intermediate-risk people, to test for atherosclerosis in the arteries supplying blood to the brain
• Microalbuminuria, in intermediate-risk people or those with high blood pressure or diabetes, to test for early signs of kidney damage
• Conventional echocardiography, in people with high blood pressure, to check for thickening of the heart muscle
• Nuclear stress testing, in people with diabetes or a strong family history of heart disease, when previous tests suggest a high risk for heart disease
• Exercise ECG stress test, in intermediate-risk people, for example, before starting a vigorous exercise program
• Hemoglobin A1c, in people with or without diabetes, to gauge average blood sugar levels over time
• Lipoprotein-associated phospholipase A2, in intermediate-risk people
Tests that have no benefit in people without symptoms of heart disease:
• Genetic testing
• So-called “advanced” lipid testing (e.g., apolipoproteins, particle size and density)
• Natriuretic peptide levels
• Coronary computed tomography angiography
• Magnetic resonance imaging for detection of vascular plaque
• Stress echocardiography
• Flow-mediated dilation
• Measures of arterial stiffness
“Knowing whether a person is at low, intermediate or high risk helps a physician tailor therapy for that specific person,” Greenland said. “There are a lot of tests out there and a lot of claims that these tests are valuable for risk assessment. This guideline puts it all in perspective.”
For more information: www.cardiosource.org/ACC