Los Angeles ? A new generation of blood tests can quickly and reliably show if a person is having a heart attack soon after chest pains start — a time when current tests are not definitive, two studies found.

The newer, sensitive tests give a much better way to tell who needs help fast. Each year, 15 million people in the United States and Europe go to emergency rooms with symptoms of a heart attack, but most are not truly suffering one.

Those having a heart attack need to have blocked arteries opened quickly to limit damage to the heart muscle from lack of blood.

Doctors currently have two main ways of diagnosing a heart attack. They can use an electrocardiogram, or EKG, to measure the electrical activity of the heartbeat for abnormalities. But that test is not always conclusive.

Doctors also use blood tests to detect elevated levels of a heart muscle protein known as troponin — a sign of heart muscle injury. A drawback with the older troponin tests is they take longer to detect increased troponin levels and by that time, heart damage may have already occurred.

Two European studies published in today’s New England Journal of Medicine found that the newer blood tests can improve early diagnosis of a heart attack soon after a person feels chest pain. The studies looked at four tests made by Abbott Laboratories, Roche and Siemens AG. The Abbott and Siemens tests are approved for use in the United States.

The accuracy of the newer tests was 94 to 96 percent compared with 85 to 90 percent for the older tests.

Mayo Clinic cardiologist Dr. Allan Jaffe advocates using the newer tests. Several doctors said the new tests do not cost more than the older versions they are replacing, and are usually covered by insurance.