Health
Reframing Framingham: New evidence prompts another look at cardiovascular risk algorithms
■ Significant effort is focused on improving precision of the risk-scoring system based on Framingham Heart Study data.
By Victoria Stagg Elliott — Posted Dec. 1, 2008
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The Framingham Risk Score, the crystal ball that helps physicians determine who is most and least in need of intervention to reduce the chance of a heart attack, is the subject of increasing debate over how to make it more accurate.
"We are humbled when patients at low risk have events, and we know that the sensitivity of the score is a problem," said James De Lemos, MD, a cardiologist and associate professor of medicine at the University of Texas Southwestern Medical Center at Dallas.
A version of the calculator, a product of six decades of research conducted as part of the Framingham Heart Study, was first proposed in several papers appearing in 1976 in the American Journal of Cardiology. The articles detailed how various factors could be used to profile an individual patient's risks. The goal was to identify those most in need of prevention and give peace of mind to those who may have one elevated factor but otherwise are healthy.
"The importance of risk stratification is that it helps you focus without needlessly alarming or falsely reassuring people," said William Kannel, MD, MPH, then the director and now a senior investigator with the project.
Subsequent versions have been published over the years. The most recent one was in the May 12, 1998, Circulation. That risk calculator iteration was then simplified and incorporated into a report by the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, which was published in the May 16, 2001, Journal of the American Medical Association. The current assessment incorporates age; total and HDL cholesterol; smoking status; systolic blood pressure; and whether a patient is taking an anti-hypertensive drug. Experts believe this tool is one of the reasons heart attack death rates have decreased. Still, a great deal of talk focuses on the tool's next revision.
"The risk algorithm should continually be re-examined if new evidence comes along," said Christopher O'Donnell, MD, associate director of the Framingham Heart Study. "And I think there are three areas that are going to frame the next decade of risk assessment -- blood biomarkers, vascular imaging and genetic markers."
Experts also say an update is due for reasons beyond the fact that time has passed and additional data are available. The focus of risk assessment is changing, with researchers wanting to devise one tool to determine the risk of all cardiovascular conditions, not just myocardial infarction. In addition, a great deal of work is going into attempts to design more accurate assessments of those identified as having intermediate risk.
A paper published in the Feb. 14, 2007, JAMA by a group at Brigham and Women's Hospital in Boston, and another online Jan. 22 in Circulation by Framingham researchers, outlined strategies to determine the 10-year risk of any cardiovascular event. The JAMA paper, for instance, outlined the Reynolds Risk Score for women, incorporating traditional risk factors along with family history and C-reactive protein, both of which are the most likely candidates to be included in future versions of Framingham. Approximately 40% to 50% of women at intermediate risk were reclassified as having a high or low chance of a cardiovascular event. A men's version was released at the American Heart Assn. meeting in New Orleans last month.
"The bottom line of both [Framingham and Reynolds] risk scores is getting the right drug to the right patient at the right time," said Paul Ridker, MD, lead author of the JAMA paper and director of the Center for Cardiovascular Disease Prevention at Brigham and Women's Hospital. "The majority of heart attacks and strokes occur in apparently healthy men and women of intermediate risk. How can we better define high and low risk within the intermediate risk group? We did it with greatly improved accuracy by adding two simple things to do a better job of getting patients stratified."
Researchers also want to create tools that don't require blood draws or multiple patient visits. The more recent Circulation document provided two means of risk assessment. One relied on the usual Framingham risk factors, and the other substituted body mass index for cholesterol numbers.
