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New Blood Test for Heart Attacks Developed With Potentially Greater Sensitivity

NEW YORK (360Dx) – A new blood test may be more sensitive in detecting damage caused by heart attacks, according to a new study.

Currently, if a heart attack is suspected, clinicians examine levels of biomarkers like cardiac troponin. If those levels exceed the 99th percentile, then the patient is diagnosed with a myocardial infarction. But researchers from King's College London noted that nearly half of patients with suspected cardiac events fall in an intermediate risk group based on troponin levels and that some groups have advocated altering that cutoff.

In a new paper appearing Tuesday in Clinical Chemistry, the researchers reported that these cutoff levels are near the limits of detection of troponin assays and that the cardiac myosin-binding protein C might be a more sensitive marker of cardiac cell death.

"This has the potential to transform the way we diagnose heart attacks in the 21st century," co-first author Tom Kaier from King's College London said in a statement.

Kaier and his colleagues spiked rat cardiac myocytes, rat myocardium, and human myocardium into human serum samples at different concentrations and analyzed their cardiac troponin and cardiac myosin-binding protein C levels using commercial assays from Abbott, Roche, and EMD Millipore.

Based on this, they found that that there was a linear correlation between the number of rat cardiac myocytes and the concentration of cardiac troponin that could be detected. Similarly, they reported that for human myocardium, both cardiac troponin and cardiac myosin-binding protein C levels correlated with myocardium mass.

In particular, Kaier and his colleagues found that between 42 milligrams and 25 milligrams of the human heart, depending on the assay used, had to undergo cell death for cardiac troponin levels to reach the 99th percentile cut off. For the Abbott test, the 99th percentile is 26 nanograms per liter, while the 99th percentile for the Roche test is 14 nanograms per liter.

These values, the researchers noted, fall very close to the limits of detection for the assays. For the Abbott test, the limit of detection is 1.9 nanograms per liter, and it is 5 nanograms per liter for the Roche assay.

They estimated that between 3 milligrams and 9 milligrams of human myocardial necrosis would be needed to push cardiac troponin levels over these assays' limits of detection.

However, cardiac myosin-binding protein-based testing was more sensitive, the researchers reported.

Fifteen milligrams of the human heart had to undergo cell death for cardiac myosin-binding protein-levels to reach its 99th percentile cut off, using the EMD Millipore test. Its limit of detection, meanwhile, is 0.4 nanograms per liter and the researchers estimated that 0.07 milligrams of human myocardial necrosis would be needed for cardiac myosin-binding protein to reach that point.

A more sensitive test like this, they said, could limit the number of patients who are unnecessarily given blood-thinning medications, as well as decrease unneeded overnight stays at the hospital.

"The main challenge for doctors is identifying who is having a heart attack, so that people can be treated quickly and effectively," added Nilesh Samani, the medical director of the British Heart Foundation, in a statement. "It's also important that we can quickly and confidently rule out a heart attack in people with chest pain from other causes. If found to be effective, this new approach could ensure thousands of patients get lifesaving treatment more quickly."