C-reactive protein, or CRP, is released as part of the human body's inflammation response. Infections and inflammation caused by various illnesses can cause CRP levels in the blood to rise. Abnormal fatty deposits on the interior walls of arteries that are prone to rupture and cause heart attacks may also cause higher levels of CRP, which is why the protein has been touted recently as a means to determine the relative risk of heart disease in some patients.
Current recommendations for CRP testing use the same cut points to determine risk for everyone. But one size may not fit all, and there may be important differences between genders and races. A study by UT Southwestern researchers, appearing in the Journal of the American College of Cardiology, examines these differences.
"Our goal was to determine the distribution of CRP levels among different genders and races," said Dr. Amit Khera, assistant professor of internal medicine and lead author of the study. "CRP as a risk factor for cardiovascular disease has been studied mainly in white men and in research groups that do not necessarily represent the community at large. The recommended thresholds of CRP may not appropriately reflect CRP distributions for black men and women."
Researchers measured CRP levels in 2,749 men and women ages 30 to 65. They found that patients with a higher body mass index, a measurement of obesity, had correspondingly higher levels of CRP. The study also found that women typically had much higher levels of CRP in their blood than men, and blacks had higher levels of CRP than white patients. CRP levels in white women were also higher than those in black men. Black men, however, have disproportionately higher rates of cardiovascular disease than white women.
"Our study was a snapshot of a population, but it showed that white women have higher levels of CRP than both black and white men. Since white women have lower rates of cardiovascular disease, this study raises some questions about how best to use CRP in the real-world setting." said Dr. Khera. "We need more research to determine if these differences translate into differences in cardiovascular events."
Dr. Khera added it's possible that different thresholds would need to exist between men and women to more accurately determine the risk of heart disease. It may also be that reliance on CRP for risk assessment in black patients may overestimate the risk for cardiac and vascular events, as more than one-half of these patients had elevated levels. But there are currently few studies of CRP in black patients.
Dr. James de Lemos, assistant professor of internal medicine and the study's senior author, said: "This is a large study that highlights potentially important race and gender differences in CRP levels. The most striking finding was the observation that almost two-thirds of black women had CRP levels above the Centers for Disease Control-defined high-risk threshold. These differences may have implications for the broad use of CRP testing."
Long-term studies are needed to see if increased CRP levels in the blood lead to heart disease in a large and diverse population. If so, it may become necessary to adjust CRP levels according to race and gender, Dr. de Lemos said.
This research is part of the Dallas Heart Study – a multiethnic, population-based study of more than 6,000 patients in Dallas County designed to examine cardiovascular disease. The Dallas Heart Study is funded by the Donald W. Reynolds Foundation.
Other UT Southwestern researchers involved in the CRP study included: Drs. Darren McGuire, assistant professor of internal medicine; Sandeep Das, postdoctoral fellow; Wanpen Vongpatanasin, associate professor of internal medicine; Frank Wians, professor of pathology; and Scott Grundy, professor of internal medicine and director of the Center for Human Nutrition. Researchers from Brigham and Women's Hospital, Boston, also contributed.
The C-reactive protein measurement study was supported by a grant from Roche Diagnostics.
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Journal
Journal of the American College of Cardiology