The blood assay detected the hormone B-type natriuretic peptide, which is released by ventricular tissue as blood pressure rises, signaling a failing heart. The test 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 affects nearly 5 million Americans, with more than 500,000 new cases each year. Patients can be treated through medication and lifestyle changes, but the five-year survival rate is only about 50 percent. Previously, emergency-room physicians have needed to use tools such as echocardiograms and chest X-rays to diagnose failure, and even then, after a typical wait for results of two or more hours, the results may be inconclusive.

Dr. Maisel noted that with the blood hormone 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 blinded to other test results were able to correctly diagnose congestive heart failure in nearly 83 percent of cases using only the results of the B-type natriuretic peptide test. When physicians could combine test results with other clinical markers-signs and symptoms such as shortness of breath, peripheral edema, or findings from other lab tests--- the accuracy rate climbed to 90 percent and above. By itself, blood hormone levels were more accurate than any other single test in identifying congestive heart failure as the cause of symptoms.

The B-type natriuretic peptide 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 congestive heart failure in up to 98 percent of cases and then could proceed to diagnosing and treating the real cause of symptoms.

Partial findings from the multinational study were presented earlier this year at the annual scientific meeting of the American College of Cardiology.