PHILADELPHIA — The Framingham risk score does a poor job of estimating future risk for cardiovascular disease events in patients with rheumatoid arthritis, according to a review of 550 unselected patients drawn from the general population.
Results from a second study reported at the annual meeting of the American College of Rheumatology suggested that adding three more risk markers (carotid disease assessment with ultrasound, erythrocyte sedimentation rate, and cumulative steroid dose) to the standard Framingham risk score (FRS) could significantly improve prognostic accuracy for coronary disease in patients with RA. And findings from a third study presented at the meeting indicated that treatment with methotrexate is an effective way to cut coronary disease risk in RA patients.
To assess the prognostic value of the FRS, Cynthia S. Crowson and her associates at the Mayo Clinic in Rochester, Minn., used data collected for the Rochester Epidemiology Project from residents of Olmsted County, Minn. They included 550 people who presented during 1988-2008 with incident RA that matched the 1987 RA criteria of the American College of Rheumatology and who also had no history of cardiovascular disease at the time of their initial RA diagnosis. The researchers calculated an FRS for each of these patients based on their medical records and using a revised FRS (introduced in 2008) that predicted risk for cardiovascular disease events including stroke and peripheral artery disease as well as coronary disease (Circulation 2008;117:743-53). The FRS estimates a person's risk for an event during the subsequent 10 years.
The Mayo researchers then compared the predicted rate of cardiovascular disease events against the actual rate observed during the first 10 years following RA diagnosis. The study group included 491 RA patients who were aged 30-74 years, and 59 others who were aged 75 years or older. The FRS is designed for application to adults younger than 75 years.
Among the 341 women aged 30-74 years, the average predicted event rate was 5%, and the actual observed rate was 11%. Among the 150 men in this age range, the predicted rate was 12% and the observed rate was 26%, Ms. Crowson, a biostatistician at the Mayo Clinic, reported in a poster. The researchers used a regression model to calculate a standard incidence ratio, in which the ratio of actual to expected events was 79% in women and 56% in men. Both differences were statistically significant. Further analysis showed that the largest differences between observed and expected rates were in women aged 55 years or older and in men aged 45 or older.
Although the FRS is not designed for use in people older than 74 years, Ms. Crowson and her associates applied the same analysis to the 59 RA patients in this age group. The results again showed a significant excess of observed events over expected events. In women, the observed event rate was 57%, compared with an expected 14% rate. In men, the observed rate was 87%, compared with an expected rate of 37%.
The findings “underscore the need for [a more] accurate tool to predict the risk of cardiovascular disease in RA patients,” the researchers concluded. They had no financial relationships to disclose.
One way to improve cardiovascular risk assessment in RA patients may be to add additional risk factors to the FRS. A poster presented by Dr. Inmaculada del Rincon, a rheumatologist at the University of Texas Health Sciences Center in San Antonio, and her associates explored one way to do this. They compared the correlation between standard FRS assessment and an enhanced assessment model for predicting the risk of acute coronary syndrome events in 599 RA patients. None of the patients in the study had a history of cardiovascular disease at the time the study began. During an average 5 years of follow-up, 66 patients had acute coronary syndrome events.
To enhance the predictive power of the FRS, they added measures of carotid plaque and intima-media thickness by carotid ultrasonography, erythrocyte sedimentation rate, and cumulative glucocorticoid dose. The analysis showed that the standard FRS accounted for 70% of the events observed in the patients. The three additional risk markers boosted this rate to 76%, a statistically significant improvement, reported Dr. del Rincon and her associates in their poster.
A third poster at the meeting reviewed the ability of treatment with methotrexate to reduce cardiovascular risk in RA patients. Dr. Janice Gupta, a rheumatologist at Tufts Medical Center in Boston, and her associates reviewed the medical literature for studies that compared the ability of methotrexate to lower cardiovascular events against other RA treatments. They identified six studies published during 2002-2007 that made this comparison. The studies involved a total of about 162,000 RA patients. The results showed a consistent pattern of reduced cardiovascular events in the patients who received methotrexate. The event risk was generally reduced by 15%–20%, compared with other RA treatments; the researchers did not calculate an overall summary risk-reduction rate.