Ask the Expert: C-Reactive Protein Test and Undiagnosed Heart Disease
For the past 3 or 4 years, my internist has done a C-reactive protein test on me. My most recent high-sensitivity CRP was 3.1, which she says is high and should be below 2.5. It's been over 5 in the past. I have no history of heart disease in my family (other than my father having a fatal aortic aneurysm), am 5'5" tall, 125 lbs., total cholesterol around 190 (usual) to 212 (most recent). Can this reflect ANY inflammation--even that due to muscle injuries? Every time I've had the CRP test, I've had either a recurring shoulder injury or back injury, but was on anti-inflammatories at the time. Should I be worried about undiagnosed heart disease, or could the elevated CRP be due to shoulder inflammation?
Your question is a very current one. I receive numerous requests from people (patients and others) to evaluate long panels of tests that they have had done in an effort to diagnose problems before they occur. These are often very expensive panels of blood tests with numerous biomarkers, histocompatibility studies, and scans of one type or another. Sometimes they are associated with "spa" type or "alternative" medicine encounters. Just as often they are associated with the publication of a scientific article that convinces some physicians that a test might have some value in the clinical practice of medicine. The test is most often sold as more useful than it actually is. In the case of C reactive protein it is sold as a test to help the physician convince someone who is not accepting a need to treat high cholesterol that such treatment would be more helpful. After all, two abnormal tests are more convincing then one.
C-reactive protein is an inflammatory protein. This means that it increases whenever there is an inflammation of any type. The ultra sensitive (high-sensitivity) C reactive protein that has been sold as a wonderful test to screen for risk of heart disease should not be used within one month of any inflammatory illness and to my mind should not be considered a screening test in low risk individuals except in research studies. As far as I am concerned there is virtually no reason to use this test clinically and I still get upset that my mother ended up having her high sensitivity C reactive protein checked at age 86 when she fell and fractured her hip. What could they possibly have expected to learn from it? Although "inexpensive" tests such as this is part of the reason that health costs keep rising with no end in sight.
C reactive protein is what many consider a "biomarker." These "biomarkers serve 2 potential roles: they provide insight into the pathophysiology of disease" in other words why does something bad happen, "and they aid clinical decision making by clarifying diagnosis, prognosis, or response to therapy. Fulfillment of one role does not ensure fulfillment of the other." The comments in quotes are from Dr. T. J. Wang in a recent editorial in the prestigious scientific journal Circulation (published by the American Heart Association) in reference to some other biomarkers that are far better founded in science than C reactive protein.
A bit more data on "markers of risk" is needed. Did you know that some of the "markers" that medicine has discovered over the years are in fact linked to other things that we do, or how we look? Perhaps you have heard of some of these "markers": C-reactive protein (CRP), fibrinogen, intercellular adhesion molecule-1, interleukin-6 (IL-6), P-selectin, and tissue necrosis factor receptor-2. Isoprostanes and monocyte chemoattractant protein-1 (MCP-1). In the ordinary course of things, none of these should be part of your blood tests. But all are related to your total body fat, body mass index, waist size, sex, age, smoking, aspirin, alcohol intake, blood pressure, diabetes, menopausal status (women only), hormone replacement therapy (women only), and physical activity. A relatively small increase in adipose (fat) tissue corresponds to an increase of 1.7 mg/L in CRP concentration among the women, with a similar but smaller increase for men.
Now, getting back to the question: "I have no risk factors" that should be stated as "I do have a risk factor" if ANY first degree relative had an early cardiovascular event (an aneurysm counts). When we tabulate our risk, the biomarkers do not count as much as our true reflection in the mirror (and it had better not be holding a cigarette).
Please keep in mind that this blog is for discussion purposes only and one should always discuss diagnoses and treatment with their individual provider.
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