Doctors have won federal approval of a new blood test to help them tell which patients suffering chest pain aren't really having a heart attack.
Making that diagnosis can be surprisingly difficult.
Up to 5 million people go to U.S. emergency rooms each year complaining of chest pain, but only about one in five is having a heart attack, according to the Food and Drug Administration.
Other ailments, from severe indigestion to gallstones, can mimic a heart attack - and up to half of chest-pain patients have atypical symptoms or test results that make diagnosis a challenge, said Dr. Steven Gutman, FDA's chief of clinical tests. In such cases, it can take from eight to 24 hours before emergency room doctors are sure the person's heart is OK and send him or her home.
On Friday, the FDA approved a simple blood test that, when added to heart checks, could greatly improve doctors' ability to rule out a heart attack and send those patients home sooner. The $30 test, made by Ischemia Technologies Inc. of Denver, uses the metal cobalt to hunt changes in a blood protein that occur during a heart attack.
Today, two tests are standard for heart-attack detection: an EKG to measure the heart's electrical activity, and a blood test that detects troponin, a protein present in the blood after a heart attack.
In a study of 200 patients, doctors were 50 percent accurate in ruling out a heart attack using just an EKG and troponin test. But when they added the new test, doctors accurately ruled out a heart attack 70 percent of the time, the FDA said.
How does the test work? A blood protein called albumin undergoes changes in its structure during a heart attack and certain other illnesses. In 1995, a Denver emergency room physician discovered that when cobalt was added to a blood sample, more of the metal would bind to normal albumin than to the changed albumin of a heart-attack victim, said Robin Daigh, vice president of Ischemia Technologies.
The company created a way to measure that cobalt-albumin reaction using chemical-analyzing equipment standard in hospital laboratories.
But the new test must be used with standard heart-attack tests. It's far from perfect, so using it alone could prove deadly, FDA's Gutman said.
Within a few weeks, the test will be available in hospitals that participated in FDA-required research on the product, including the Medical College of Virginia and University of Pennsylvania. Sales will later expand to other hospitals, Daigh said.
By Lauran Neergaard