A more sensitive test is now being used to look for evidence that a person has had a heart attack. However, experts do have a few words of caution.

Doctors will tell you that the longer you go without treatment after a heart attack, the more your heart muscle is damaged.

In the hopes of getting patients treated more quickly, the Food and Drug Administration (FDA) approved a test last year that can detect evidence of a heart attack twice as fast as previous tests.

While experts have been waiting for this new test for years, some warn there is still reason to be cautious about relying too much on this new test.

The test measures for a protein called troponin. This protein is released when a heart muscle is damaged.

In a study published last month looking at low-risk patients, researchers found that the new FDA approved high-sensitivity troponin test could help doctors identify patients having a heart attack in under three hours as opposed to six to nine hours under less sensitive troponin tests.

This high-sensitivity troponin assay has been used in Europe since 2010, but it wasn’t approved by the FDA until last year.

Heart disease is a major concern in the United States with 735,000 Americans having a heart attack annually, and 610,000 deaths attributed to heart disease.

As a result, finding ways to detect and treat heart attacks early is key.

Dr. Frederick Korley, assistant professor of emergency medicine at the University of Michigan, explained how heart attacks are often diagnosed.

“Troponin is the way heart attacks are diagnosed, it’s used in addition to the ECG,” he said. “But very few people having a heart attack actually have signs of the heart attack on the ECG, so for the vast majority we rely on the blood test troponin.”

The protein is released when the heart muscle is damaged.

Korley said because of how sensitive the tests are, doctors can see if a patient is likely having a heart attack within a few hours. Prior to this test, it often took more than six hours for enough troponin to be released to be detectable on a test.

“They’re measuring the same thing, but the new [test] is able to measure 10 times lower concentration of troponin, than in the past,” Korley told Healthline.

But Korley and other experts caution that doctors shouldn’t rely too heavily on this test when determining who has a heart attack.

Dr. Puneet Gandotra, a cardiologist at Northwell Health’s Southside Hospital in New York, said this new test is a “great tool” and can significantly cut down on the time patients wait in the emergency room for test results.

“This is a great mechanism for emergency rooms because you are able to pick up an acute coronary syndrome or a heart attack in a patient a lot earlier and a lot faster than you would otherwise,” he said.

However, he warned that the test may be so sensitive that it may pick up abnormal levels that aren’t signs of a heart attack.

As a result, patients may undergo unnecessary treatment for a heart attack or be stuck in the hospital for longer over concerns they’re having a heart attack.

In an editorial in JAMA Cardiology, Korley warned that doctors need to be cautious when using this test to diagnose a heart attack.

“We still have to figure out the right cutoffs to use,” he said. “Based on the current study, essentially we’re learning that the cutoff for abnormal is different in the U.S. from Europe.”

The study found that in the United States, those with troponin levels of 19 nanograms per liter would be considered abnormal or likely to have a cardiac event. However, in Europe that number is lower at 14 nanograms per liter.

“We’re going to need to be more savvy in interpreting these results,” Korley said.

He also said that doctors who don’t detect troponin within an hour or two hours of symptoms may be inclined to believe a patient isn’t having a heart attack.

“We still have to be careful with those who have symptoms and come to the emergency department very shortly afterward,” Korley said.

He explained that tests within the first two hours of a cardiac event may not be sensitive enough to reveal that something is wrong.

Korley also said that since the test is new, doctors will also need to be careful when treating women who exhibit signs of a heart attack.

Since the 19 nanograms is the same cutoff for men and women, Korley worries that women may be at a “disadvantage” or may be for overlooked if they have a lower troponin level.

“This problem could potentially be a bigger deal in the United States, where we’re using a higher cutoff,” he said. “We still need the data to learn about this some more.”