Troponin, located at the double helix part of the tropomyosin on the thin myofilament of striated muscle, is a complex consisting of the following three single polypeptides: troponin I (Tnl), troponin C (TnC) and troponin T (TnT).
TnC has no myocardial characteristic. Both Tnl and TnT can be divided into 3 types: cardiac myocyte troponin, slow skeletal muscle contraction troponin and quick skeletal muscle contraction troponin. Cardiac troponin I (cTnl) and cardiac troponin T (cTnT) are cardiac specific calcium binding proteins and normally with very low concentration in the blood. These Troponin polypeptides which show high sensitivity and cardiac-specificity for myocardial necrosis, will be released into blood circulation and make the concentration elevated if there is any damage of the cardiac myocytes.
Compared with cTnl, cTnT is easily affected by other factors, such as renal function disorder. Patients with chronic renal insufficiency often appear false positive for cTnT test, while the cTnl detection appears negative at the same time. Thus, S-cTnl detection is more accurate without delay for the diagnosis of early Acute Coronary Syndrome (ACS).
According to the new definition for Ml (myocardial infarction) in the ESC I ACCF I AHA I WHF 2007, when blood cardiac troponin concentration is higher than the 99th percentile of the reference population, together with the performance of myocardial ischemia (with symptom, ECG change or Imaging results),it can be diagnosed as myocardial infarction. If the reagent can meet the demand which means the diagnostic cut point at the 99th percentile of the reference population give an optimal coefficient of variation(CV) of less than or equal to 10%, it can be called as super-sensitive (Ultra) troponin detection reagent.