Troponin is a protein released into the bloodstream when there is damage to the heart muscle. Elevated troponin levels can indicate a heart attack (myocardial infarction). The specific threshold for diagnosing a heart attack varies depending on the laboratory and the assay used to measure troponin. Typically, troponin levels above the 99th percentile of the normal reference range are considered abnormal. However, the clinical context is crucial in interpreting troponin levels, as other factors like kidney disease, inflammation, or strenuous exercise can also cause troponin elevation. Therefore, it's important to consult with a healthcare professional to evaluate troponin levels in conjunction with other clinical signs and symptoms.