Test Measures Very Low Levels of Heart Protein, Troponin I
By Salynn Boyles
WebMD Health News
Reviewed by Louise Chang, MD
An electrocardiogram (ECG), one of the key tests used to confirm heart damage, isn't always conclusive. When that happens, doctors may use a blood test that measures a muscle protein in the blood. If someone has high levels of the protein, known as troponin I, they are more likely to have suffered heart damage.
Now, an even more sensitive version of the test may be more helpful in ruling out a heart attack accurately and quickly, according to new research in the Journal of the American Medical Association.
Researchers from Germany's University Heart Center Hamburg who used the newly developed test were able to accurately rule out a heart attack close to 99% of the time by repeating the test.
Among the 1,818 patients in the study, the more sensitive test proved to be more effective for ruling out heart attacks than regular troponin I testing.
"This test appears to be able to detect more subtle forms of damage to the heart," says American Heart Association president Gordon Tomaselli, MD, who is chief of cardiology at Johns Hopkins Heart and Vascular Institute in Baltimore.
Over-diagnosis of heart attacks is a common issue that can lead patients to get treatments that may not be needed.
Troponin I Better Than Other Biomarkers
Both highly sensitive troponin I and the conventional version of the blood test were found to be better than the other biomarkers for confirming or ruling out heart attacks.
For the most accurate result, the test was repeated within three hours after hospital admission.
Tomaselli tells WebMD that more research is needed to validate the findings. Highly sensitive versions of the test may be so sensitive that they over-diagnose heart attacks since very low blood concentrations of the protein can be found in people not having a heart attack.
He adds that if the findings are validated, highly sensitive troponin I tests are likely to be widely used in the emergency setting.
"This test has not completely overcome the problem (of over-diagnosis), but it is very effective at ruling out heart attacks with serial testing," he says.
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