CRP, other disease-linked factors don't perform better than standard criteria, study finds
TUESDAY, June 30 (HealthDay News) -- Newer biomarkers of cardiac risk, such as inflammation-linked C-reactive protein (CRP), add little or no predictive power to older, established factors such as smoking, obesity, high cholesterol and physical activity, two major studies find.
The newer blood-borne markers have been touted as a better way of assessing heart risk, but recent studies have suggested otherwise.
In fact, the lead author of one of the new studies said his team reported essentially the same finding in an analysis of data from the Framingham Heart Study nearly three years ago.
"A lot of people said [those findings] made sense, but others said the study had limitations -- small numbers, not enough follow-up," said Dr. Thomas Wang, associate director of the Heart Failure Service at Massachusetts General Hospital in Boston.
So, he collaborated with Swedish researchers in a study with larger numbers -- more than 5,000 participants -- who were followed for a longer time, an average of 12.8 years. They looked at more offbeat biomarkers and used newer statistical methods for evaluating risk.
"The long and short of it was that we had the same conclusion -- that these biomarkers add a little bit but not a lot," Wang said. "There is not enough evidence to recommend that any of these biomarkers be routinely measured."
The six biomarkers surveyed in the study were CRP, an indicator of inflammation; cystatin C; lipoprotein-associated phospholipase 2; midregional proadrenomedullin; midregional proatrial natriuretic peptide; and N-terminal pro-B type natriuretic peptide.
Five of the biomarkers did help predict future heart problems, and three predicted problems in models that adjusted for conventional risk factors, but the improvement over usual risk factor assessments was "minimal" and "did not reclassify a substantial proportion of individuals to higher or lower risk categories," said the report, published July 1 in the Journal of the American Medical Association.
A second study in the same issue of the journal, done by British researchers at Imperial College London, looked only at CRP. That study, involving almost 130,000 people, examined genes that control blood levels of the inflammation-related molecule. The study found no association between genetically controlled levels of CRP and heart disease.
"This study suggests that development of therapeutic strategies targeting specific reductions in plasma levels of CRP are unlikely to be fruitful," the researchers concluded.
The new studies do not say that CRP is of no use in assessing heart risk, noted Dr. James A. de Lemos, an associate professor of medicine at the University of Texas Southwestern Medical Center in Dallas and co-author of an accompanying editorial.
"This study shows a modest incremental value," de Lemos said. "Other studies focusing on more homogeneous populations, such as the elderly, clearly show value."
But in general, the predictive value of the newer biomarkers is limited, he said. "In these low-risk populations, there is no 'wow' marker, no major breakthrough in terms of markers that allow us to assess risk in a generally healthy population," de Lemos said.
De Lemos does test for biomarkers in his clinical practice: "Selectively, and not across the board," he said. "I do it on an individual basis. For example, if I am on the fence about whether to use a statin [a cholesterol-lowering drug], I may measure CRP levels. It is an occasional test for me."
Despite the limited usefulness of alternate biomarkers found in these studies, "research should continue to go on in these areas, without a doubt," de Lemos said.
Wang agreed. He said it's still possible that newer biomarkers of potentially greater predictive value will be identified in the years ahead, and they should be tested.
"But the basic risk factors do pretty well, and we don't pay as much attention to these basic risk factors as we should," Wang said.
The American Heart Association has more on heart disease risk factors.
SOURCES: Thomas Wang, M.D., associate director, Heart Failure Service, Massachusetts General Hospital, Boston; James A. de Lemos, M.D., associate professor, medicine, University of Texas Southwestern Medical Center, Dallas; July 1, 2009, Journal of the American Medical Association
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