A CRP blood test for heart disease risk does not add much to the other information doctors use. A review of 52 previous studies found this result. The studies included 240,000 people. None of the people had cardiovascular disease. The test was helpful in less than 2% of people. A CRP test is a blood test. It measures inflammation in the body. Inflammation may lead to narrowing of blood vessels. This can increase a person's risk for heart attack or stroke. People most likely to benefit from heart-disease screening are those at medium risk. But in that group, regular CRP tests prevented only 1 heart attack or stroke for every 400 to 500 people screened. The study was published October 4 in the New England Journal of Medicine.
By Robert H. Shmerling, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
A screening test can save your life.
If the test result suggests that you are at risk for a disease, you can take measures to lower your risk. And if a disease, such as cancer, is already present, a screening test could detect it at an early and curable stage.
Consider colonoscopy. If your colonoscopy identifies polyps, they can be removed before they become cancerous. And if you have a small cancerous growth in your colon, it can be found and removed during a colonoscopy. This has a high rate of cure.
But, the potential benefits of screening are only as good as the screening test.
The ideal screening test:
- Is easy to perform - Urine tests and blood tests are examples.
- Can be performed noninvasively - A colonoscopy is not ideal, because it is somewhat invasive.
- Is highly accurate - The test should identify people at risk or who have a disease. It also should be able to identify people who don't have a disease, or who are at lower risk.
- Is acceptable to patients - One reason that colonoscopy rates are not higher is that many people don't want to have a colonoscopy.
Screening tests are more useful for certain diseases. Ideally, the disease should be treatable. That way, an abnormal test result can lead to effective treatment or ways to reduce disease risk in the future. The disease should be somewhat common. Screening has a bigger impact on more common diseases.
A new study examines whether the CRP test is an effective screening test for cardiovascular disease. You may have had this blood test. Many physicians use it routinely. The CRP is a measure of inflammation. And inflammation is thought to contribute to the narrowing of arteries in the body. This narrowing may lead to heart attack and stroke.
Researchers analyzed 52 studies that included more than 240,000 people without cardiovascular disease. They looked at the results of the CRP test and another measure of inflammation (called fibrinogen). They added the results to standard risk factors, such as diabetes or high cholesterol. Using all of this information, they classified people as to their risk of future cardiovascular disease and whether they needed preventive treatment.
This new analysis found that CRP added little to standard risk factors:
- The information provided by CRP screening was considered helpful in less than 2% of patients.
- Over a 10-year period among people at a medium risk of cardiovascular disease, regular CRP and fibrinogen tests could have prevented cardiovascular events in less than half of 1%. This translates to the prevention of 1 cardiovascular event for every 400 to 500 people screened. People at medium risk are those most likely to benefit from screening.
- It seems that after reviewing standard risk factors, the CRP test result rarely adds much information.
What Changes Can I Make Now?
It is important to know the risk factors for cardiovascular disease and to do what you can to reduce them. Risk factors include:
- High blood pressure (hypertension) Get your blood pressure checked regularly. If its high, limit your salt intake and lose excess weight. If necessary, take medications to lower your blood pressure.
- Smoking Commit to quit. If you have trouble quitting on your own, talk to your doctor about smoking cessation programs and medications that can help. Avoid second-hand smoke as well.
- High total or LDL cholesterol If your cholesterol profile is not ideal, talk to your doctor about your options. Changes in diet and loss of excess weight are enough for some people. But many people need medication.
- Diabetes If you have diabetes, your doctor will recommend dietary changes and losing excess weight. Often, people need medicines to lower blood sugar levels. They also may need other medicines to lower their risk of cardiovascular disease.
- Family history If you have a strong family history of cardiovascular disease, modifying the above risk factors is even more important.
If your doctor recommends a CRP (or fibrinogen) test as a screening test for cardiovascular disease, ask how the results will affect your care. For example, if you are at low risk for cardiovascular disease because you lack risk factors, will a high CRP result mean that you may need a change in care? If you already are at high risk, will your CRP result change your treatment? If the CRP result will not change your care, talk with your doctor about whether you need the test. The results of this new analysis suggest that the CRP may not be as helpful as some previous studies (and many doctors) suggested.
What Can I Expect Looking to the Future?
Researchers will continue to look for new ways to identify people at risk for cardiovascular disease. After all, its the top killer of adults in many countries, including the United States. Preventing cardiovascular disease could have a huge impact on premature deaths, suffering and medical costs.
We may learn in the future that CRP screening is useful for some people. But, if the results of this new analysis are confirmed by other studies, the popularity of CRP screening in healthy people could decrease.