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New model may help identify patients with pulmonary embolism who are at low risk of death

January 24, 2006

Looking at 10 easily obtained risk factors, including age, blood pressure and medical history, could help physicians identify patients with pulmonary embolism who are at low risk of death in the short term and therefore are candidates for outpatient treatment, according to a new study in the January 23 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Pulmonary embolism (PE) generally occurs when a blood clot that develops in the veins of the leg or pelvis becomes dislodged and results in sudden blockage of an artery in the lung. It is a major health problem in the United States, causing more than 100,000 hospitalizations in 2002, according to background information in the article. The condition can be fatal, but evidence suggests that nonmassive PE, which is not accompanied by respiratory failure or other serious complications, could effectively and safely be treated on an outpatient basis, the authors write.

Previous studies have shown that outpatient treatment for PE also could be economically beneficial-the authors estimate that if 20 percent of people with PE were treated as outpatients, up to $91 million per year could be saved in the United States alone. However, "outpatient treatment for nonmassive PE is not widely accepted because no explicit clinical criteria exist to accurately identify patients with PE who are at low risk of adverse outcomes," they write. "Therefore, we sought to develop an objective and easily applied clinical prediction rule to identify patients with PE at low risk of short-term mortality and other adverse medical outcomes who are candidates for outpatient treatment."

Drahomir Aujesky, M.D., M.Sc., University of Lausanne, Switzerland, and colleagues developed this prediction rule or model by evaluating 15,531 admitted patients who received a discharge diagnosis of PE from 186 Pennsylvania hospitals. By concentrating on 10,354 patients, they identified 10 risk factors that indicated a greater risk of short-term death (within 30 days), including an age of 70 years or older; a history of cancer, heart failure, chronic lung disease or chronic kidney disease; cardiovascular disease; altered mental status; a high pulse rate; low systolic blood pressure; and reduced oxygen saturation in arterial blood. Patients without any of these factors are considered low-risk and eligible for outpatient treatment.

The researchers then tested their model on the remaining 5,177 participants in the original study group and by using data from a previous study of 221 Swiss patients with PE. Low numbers of patients in these two groups-1.5 percent and none, respectively-who were low-risk according to the model died within 30 days, and less than 1 percent developed non-fatal complications. "This simple prediction rule accurately identifies patients with pulmonary embolism who are at low risk of short-term mortality and other adverse medical outcomes," the authors write. "Prospective validation of this rule is important before its implementation as a decision aid for outpatient treatment."

JAMA and Archives Journals