Coronary Risk Score Given to Millions of Senior
Citizens by Their Doctor May be Misleading
Simplified Framingham model could be leading to the
wrong treatment options
Sept. 10, 2010 – Multitudes of senior citizens have
watched their cardiologists tally their current health statistics and
mark down a percentage that represents their chance of a major coronary
event in the next 10 years. It is based on the simplified version of the
Framingham model, but researchers have found this method may over or
underestimate the risk for millions of Americans.
The method in question, the simplified version of
the so-called Framingham model, is used to estimate a patient's 10-year
risk of a heart attack, stroke, or other coronary event based on risk
factors such as age, cholesterol levels, blood pressure, and smoking,
according to this study directed by a researcher at the San Francisco VA
Medical Center and the University of California, San Francisco..
National guidelines recommend using the risk
estimates generated by the Framingham model to classify patients as
among one of three risk groups. Guidelines recommend more aggressive
strategies to treat cholesterol in patients classified into higher-risk
groups.
The original Framingham model uses a complicated
mathematical equation to calculate risk, while the simplified version is
based on a point system, with a certain number of points for each risk
factor.
"We thought there might be significant differences
between the two methods, which would have significant impacts on how
people are treated for cholesterol," says principal investigator Michael
Steinman, MD, a physician at SFVAMC and an assistant professor of
medicine at UCSF. "And in fact, that turned out to be the case."
For the study, which appears in the Online First
section of the Journal of General Internal Medicine, the
researchers assessed data from 2,543 subjects who participated from 2001
to 2006 in National Health and Nutrition Examination Surveys sponsored
by the Centers for Disease Control and Prevention. The subjects were
chosen to be representative of 39 million adults in the United States
for whom guidelines recommend using the Framingham method to predict
future cardiovascular risk.
For each subject, the researchers calculated risk
based on the original Framingham model and on the simplified model, and
compared the differences, "which turned out to be substantial for many
patients," says Steinman, who is senior author of the paper.
Under the point-based system, 15 percent of the
subjects were classified as being at a different level of risk than they
were under the original model. Nationwide, say the authors, 5.7 million
Americans would be placed into different risk groups using the
point-based model than they would be using the original model, with 3.9
million misclassified into higher risk groups and 1.8 million
misclassified into lower risk groups.
"Across the group, on average, these statistical
differences balance out," says Steinman. "But for individual patients,
they are potentially important. A lot of individuals would be treated
differently – either more aggressively or less aggressively – using the
point-based model."
Steinman notes that the point-based model, which
can be completed in a few minutes with pen and paper, was introduced
over a decade ago, when computers and personal digital assistants were
less powerful and not so common in private medical practices.
"While the point-based system is a substantial
improvement over having no standardized method for predicting risk, just
about any computer or PDA in use today can calculate the original
Framingham model," says Steinman. "This means that your doctor can
calculate your risk just as easily using the complex equation, which is
likely to be more accurate than the point-based system. So there's not
much reason to use the point-based system anymore in most instances."
Steinman cautions that the study was not designed
to determine the benefits or harms for individuals who would be treated
differently based on the results of the two models.
The study authors note that the next generation of
cholesterol guidelines is expected to be released in the near future,
and that point-based versions of the new risk model have already been
developed, which may result in similar misclassifications.
"With risk prediction models being increasingly
used for many different diseases and conditions, this could be a general
problem in the field of medicine," predicts Steinman. "In creating
simplified risk models, we have to be aware of the potential impact on
individual patients."
Notes:
The first author of the paper was William J. Gordon
of Weill Cornell Medical College; Jesse M. Polansky, MD, MPH, working as
an independent researcher; and W. John Boscardin, PhD, and Kathy Z.
Fung, MS, of SFVAMC and UCSF.
The study was supported by funds from the National
Institute on Aging, the American Federation for Aging Research, the
Hartford Foundation, the Department of Veterans Affairs, and the
National Institutes of Health. Some of the funds were administered by
the Northern California Institute for Research and Education.
The authors include the following disclosure in the
paper: Polansky is lead plaintiff in United States of America ex rel.
Polansky v. Pfizer, Inc., 04-cv-0704 (ERK) (E.D.N.Y.), which alleges
improper marketing campaigns to promote the point-based version of the
Framingham model in an effort to increase sales of lipid-lowering
medications. The authors have no further disclosures.
NCIRE – The Veterans Health Research Institute – is
the largest research institute associated with a VA medical center. Its
mission is to improve the health and well-being of veterans and the
general public by supporting a world-class biomedical research program
conducted by the UCSF faculty at SFVAMC.
SFVAMC has the largest medical research program in
the national VA system, with more than 200 research scientists, all of
whom are faculty members at UCSF.
UCSF is a leading university dedicated to promoting
health worldwide through advanced biomedical research, graduate-level
education in the life sciences and health professions, and excellence in
patient care.
Keep up with the latest news for senior citizens, baby
boomers
Sept. 10, 2010 – Multitudes of senior citizens have
watched their cardiologists tally their current health statistics and
mark down a percentage that represents their chance of a major coronary
event in the next 10 years. It is based on the simplified version of the
Framingham model, but researchers have found this method may over or
underestimate the risk for millions of Americans.
Says persons having myopathy with a statin should
discuss other alternatives with their physician