WEDNESDAY, March 31, 2004 (HealthDayNews) -- C-reactive protein, a marker of inflammation, isn't as good an indicator of coronary risk as some early reports had indicated, a British study finds.
"Our conclusion is that the predictive value of C-reactive protein has been exaggerated, and substantially exaggerated," said Dr. John Danesh, a professor of epidemiology and medicine at the University of Cambridge. His report appears in the April 1 issue of the New England Journal of Medicine.
"I wouldn't use the term 'exaggerated' because that implies intention," said Dr. Alan Tall, a professor of medicine at Columbia University who wrote an accompanying editorial. "I would say 'overestimated.'"
C-reactive protein has gotten a lot of attention in the past year or so, as interest in the role of inflammation in heart disease has increased. Some studies have found it to be a better indicator of risk than such established factors as high blood pressure or smoking.
"This helps bring us down to earth a little," Tall said of the new report.
The official stance on C-reactive protein as a risk factor has been cautious. Last year, an expert panel of the U.S. Centers for Disease Control and Prevention and the American Heart Association told cardiologists that measurement of C-reactive protein blood levels in people at intermediate risk was an option, not a necessity.
"That was already a soft recommendation; that it should be used in a limited way," Tall said. "Maybe this report will make its use a little less popular."
The new finding comes from what Danesh calls "the largest and most rigorous evaluation so far of the predictive value of C-reactive protein in coronary disease in the general population." It comes from the Reykjavik Study, which includes more than 18,500 Icelanders.
C-reactive protein blood levels were measured in participants at the start of the study. Those readings were used to assess the value of C-reactive protein as a predictive factor in the 2,459 people who had a heart attack, fatal or nonfatal, and 3,969 control subjects who had no coronary event over more than a decade.
A vital part of the study, both Danesh and Tall say, is that the results were rigorously adjusted to account for other established risk factors -- blood pressure, cholesterol levels, smoking, and so on.
"It now appears that measurement of C-reactive protein provides little predictive value above that of the established risk factors," Danesh said.
Those findings "are in part confirmatory of the recent work on C-reactive protein as an independent risk factor," Tall said. The new study is convincing because its large population "allows more precision in its findings" and because of the thorough treatment of other risk factors, he said.
"This helps dull the enthusiasm for measuring C-reactive protein," Tall said.
"The American Heart Association and Centers for Disease Control and Prevention recommendation acknowledged the need for bigger studies," Danesh said. "This provides just that."