C-reactive Protein: A New Screening Test for Cardiovascular Disease?
For many years now, people have been getting their levels of blood cholesterol tested to determine if they may be at risk for cardiovascular diseases and its complications, such as heart attack and stroke. Paradoxically, however, most patients who experience these complications have cholesterol levels that are reassuring. Now a new study in the November 14, 2002 issue of The New England Journal of Medicine suggests that additional testing for a substance called C-reactive protein, which indicates inflammation in the body, may help doctors more accurately determine which patients are at risk for cardiovascular disease (CVD) events.
About the Study
Researchers from Harvard Medical School studied 27,939 apparently healthy women participating in the Women’s Health Study. At baseline (between November 1992 and July 1995), the women were at least 45 years of age (average age 54.7) and free from known CVD. The women supplied detailed information about their lifestyles and medical histories, and they also supplied blood samples.
Over an average follow-up period of eight years, the researchers determined how many women developed their first cardiovascular events, including nonfatal heart attack, nonfatal stroke, clogged arteries requiring surgical treatment, and death from any cardiovascular cause. They also tested the women’s blood samples for levels of low-density lipoprotein (LDL) cholesterol (“bad” cholesterol) and C-reactive protein.
The researchers performed statistical analyses to determine how the women’s baseline levels of LDL cholesterol and C-reactive protein correlated to their subsequent development of CVD, and if one measurement was a stronger predictor of CVD development than the other.
Both LDL cholesterol and C-reactive protein levels were predictors of subsequent cardiovascular events, but C-reactive protein was a stronger predictor. In many cases, women who had LDL cholesterol levels within ranges considered “acceptable” by current guidelines (less than160 mg/dL [4.1 mmol/L] for women without other CVD risk factors and less than130 mg/dL [3.4 mmol/L] for women with other CVD risk factors), but who had elevated C-reactive protein levels, did experience subsequent cardiovascular events. The researchers also stated that LDL and C-reactive protein appeared to predict CVD risk in different subsets of women, indicating that the most effective screening methods would likely include both LDL and C-reactive protein.
In doing the analyses, the researchers accounted for other factors that could potentially influence the occurrence of CVD events, including smoking, diabetes, high blood pressure, and the use of hormone replacement therapy.
Although these findings are interesting and potentially important, there are some limitations to this study. First of all, the study was conducted only in women, so the results are not necessarily applicable to men. In addition, the researchers compared the predictive value of C-reactive protein only to LDL cholesterol, but not to other physiologic factors that may influence CVD risk, such as HDL cholesterol, triglycerides, or blood clotting factors. Finally, although inflammation is felt to be significant in the development of CVD, compared to cholesterol, the physiologic mechanism is not well established.
How Does This Affect You?
Cardiovascular disease is a very significant public health problem—heart disease is the number-one killer of American men and women. Therefore, any advances scientists can make in improving methods for CVD screening could have major implications. The results of this study are intriguing and are likely to spur even more research on the potential value of C-reactive protein in predicting CVD risk. Doctors are unlikely to begin screening for C-reactive protein based on this one study. However, given the results of previous studies, expert panels that set guidelines for CVD prevention are likely to consider adding screening for C-reactive protein in the near future.
Each person’s risk for CVD varies widely, based on a variety of factors. To manage your own risk for CVD, talk to your doctor or healthcare provider about what your individual risk factors may be and which screening tests may be most useful. And remember that the lifestyle choices you make every day, such as eating a healthful diet, getting regular exercise, and not smoking, will do far more to lower your risk for CVD, then checking your C-reactive protein level.
National Heart, Lung, and Blood Institute
American Heart Association
Ridker PM, Rifai N, Rose L, et al. Comparison of c-reactive protein and low-density lipoprotein cholesterol levels in the prediction of first cardiovascular events. N Engl J Med . 2002;347:1557-1565.
Mosca L. C-reactive protein: to screen or not to screen? [Editorial]. N Engl J Med . 2002;347:1615-1617.
Last reviewed Nov 22, 2002 by ]]>Richard Glickman-Simon, MD]]>
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