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Troponin I in the blood
Last reviewed: 04.07.2025
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Reference values (norm) for troponin I content in blood serum are 0-1 ng/ml.
Troponin I is a structural protein of the muscle troponin complex with a molecular weight of 26,500 Da. Troponins I, like troponins T, of cardiac and skeletal muscles differ significantly in their amino acid sequence. This made it possible to create diagnostic kits for cardiac isoforms of these troponins. For troponin I, the difference in amino acid sequence between the cardiac and skeletal isoforms is approximately 40%. Troponin I and troponin T are components of the contractile apparatus, that is, structurally related proteins of cardiomyocytes; while proteins dissolved in the cytosol (myoglobin) are relatively quickly washed out of the necrosis zone, destruction of the contractile apparatus of cardiomyocytes is more prolonged in time, therefore, an increase in the concentration of troponins persists up to 8-10 days after the onset of myocardial infarction. Troponin I is a highly specific marker of myocardial infarction. The concentration of troponin I in the blood increases 4-6 hours after the onset of myocardial infarction (in 50% of patients), reaches a maximum on the 2nd day and returns to normal between the 6th and 8th days. The average values of troponin I concentration in the blood on the 2nd day of myocardial infarction are 80-100 ng/ml. When assessing the results of troponin I testing, it is important to remember that the cutoff values of its concentration (myocardial infarction and non-myocardial infarction) are 2.5 ng/ml. The content of troponin I increases in patients with unstable angina with the development of micronecrosis. With stable angina, an increase in the content of troponin I is not observed.
Unlike troponin T, the concentration of troponin I does not increase in patients with renal failure, massive muscle damage and disease.