The study, led by a Department of Veterans Affairs (VA) cardiologist, appears in the July 18 issue of the New England Journal of Medicine.
"This is extremely novel and exciting. There has never been a blood test for congestive heart failure before," said lead investigator Alan Maisel, M.D., director of the Coronary Care Unit at the VA San Diego Health Care System and professor of medicine at the University of California, San Diego.
The test, developed by San Diego-based Biosite, Inc., detects elevated levels in the blood of a hormone called B-type natriuretic peptide (BNP). The hormone is released by the heart ventricles when pressure rises, signaling a failing heart.
The BNP test received approval by the Food and Drug Administration (FDA) in 2000, and is currently the only blood test cleared by the FDA as an aid in diagnosing congestive heart failure. It proved effective in an earlier pilot study by Dr. Maisel and is already in use in more than 300 hospitals in the United States.
Congestive heart failure (CHF) occurs when the heart can't pump enough blood to supply the rest of the body. As a result, blood backs up in the body, mainly the liver, lungs, hands and feet. Physical symptoms include shortness of breath, coughing and swelling.
The condition is different from heart attack, where the blood supply to the heart itself is restricted. CHF affects nearly 5 million Americans, with more than 500,000 new cases each year. People with CHF can be treated through medication and lifestyle changes, but the five-year survival rate is only about 50 percent.
When patients arrive at the emergency room with shortness of breath, doctors must first determine the cause before they can prescribe effective treatment. They must rule out for instance, lung disease or kidney failure.
Before the BNP test, they had to wait--sometimes up to three hours--for the results of various clinical tests, such chest X-rays, echocardiograms and CT-scans. Even then, these tests are not conclusive. Dr. Maisel said that with the BNP test, "Two drops of blood can get you results in 15 minutes. This test helps saves lives and time."
In the multinational trial, held at seven hospitals in the United States, France and Norway, doctors were able to correctly diagnose CHF in nearly 83 percent of cases, using only the results of the BNP test. They were blinded to the results of other tests.
When they combined the results with other clinical markers--physical symptoms such as shortness of breath, swollen ankles, or findings from other lab tests--the accuracy rate climbed to 90 percent and above. By itself, BNP levels were more accurate than any other single test in identifying CHF as the cause of symptoms.
The BNP test also has a high "negative predictive value." In the trial, doctors using only the results of the blood test were able to correctly rule out CHF in up to 98 percent of cases, and proceed to diagnosing and treating the real cause of symptoms.
Partial findings from the BNP multinational study were presented earlier this year at the annual scientific meeting of the American College of Cardiology.
In addition, Dr. Maisel published results in the Sept. 15, 2001, American Journal of Cardiology from a study of a different rapid blood test, used for diagnosing heart attack in the emergency room. That test, also made by Biosite, checks the blood levels of three cardiac enzymes released by distressed heart tissue. Maisel and colleagues used the test over nine months on nearly 1,300 patients with signs of heart attack, and achieved a 40 percent drop in critical care admissions, and a 20 percent drop in overall hospital admissions.
The multinational trial of the BNP test was conducted in the emergency rooms of the VA San Diego Health Care System; Henry Ford Hospital in Detroit; Hospital of the University of Pennsylvania, Philadelphia; University of Cincinnati Medical Center; Hartford Hospital in Connecticut; Hospital Bichat in Paris, France; and Ulleval University Hospital in Oslo, Norway.
The trial was supported by Biosite, the maker of the BNP test. Maisel is a consultant for the firm and has received research support from it in the past.
Journal
New England Journal of Medicine