What is the Normal Troponin Range?

Troponin is a term used to describe a complex of 3 specific proteins called troponin I (TnI), troponin C (TnC) and troponin T (TnT). The protein complex plays a vital role in allowing contraction of the cardiac and skeletal muscle. This is the reason why high levels of troponin, found via a troponin blood test, can be an indication of myocardial infarction or myocardial damage.

Troponin T and troponin I are concerned with only the cardiac muscles. Hence, verifying their levels can help in gathering valuable data about the heart health as well as in diagnosis of conditions afflicting the myocardium.

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Function of troponins

  • Troponins are controlling proteins that are important to the process of contractions of the heart muscles. The process typically consists of alterations in the concentration of calcium occurring within the cells, which is what facilitates the relaxation and contraction of the muscles.
  • Troponin C attaches to the calcium ions to create certain alterations in troponin I. Troponin T then forms the troponin-tropomyocin complex by binding to a protein known as tropomyosin. The troponin-tropomyocin complex occurs inside the folds of the actin filaments.
  • Troponin I is the protein which sticks to actin in the form of slim filaments in the cells of the muscles and aids in securing the actin-tropomyocin complex. Each time calcium ions pass into the cytoplasm and continue towards the myosin and actin filaments, they bind themselves to the molecules of troponin-tropomyocin. This then results in an alteration in the shape or form of troponin, which then leads to displacement of tropomyosin from its original place.
  • After the exposure of the myosin-actin binding areas, myosin and actin react with one another. This is what trigger the contraction of the muscle. Troponin goes back to its original shape when the calcium ions pass out from the cytoplasm. As actin and myosin are unable to react with each other due to the absence of the myosin-actin binding sites, there is relaxation of the muscle.

When and why is a troponin test ordered?

  • Any kind of damage to the heart muscle can trigger the release of troponin proteins into the blood stream. Hence, a troponin test is used as a diagnostic tool for verifying the occurrence of any signs of damage to the heart muscle.
  • In most cases, a doctor will order for a troponin test to check if there has been a heart attack. He/she may ask for the test if a patient complains of chest pain and other symptoms of a cardiac arrest. The test is conducted again 2 more times over a period of the following 5 to 24 hours.
  • The health care provider may also ask for a troponin test if the patient has a deteriorating case of angina without any additional signs of a cardiac arrest. It may be noted that angina refers to chest pain which may occur due to deficient flow of blood to the heart.
  • A troponin test may also be carried out to diagnose and examine other causes of cardiac trauma and injury. Sometimes, it may be conducted along with additional cardiac marker tests like myoglobin or CPK isoenzymes.

Some of the conditions that could result in elevated levels of troponin proteins are listed below:

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  • Varied conditions and disorders of the heart such as supraventricular tachycardia; myocarditis, i.e., heart muscle inflammation often because of a viral infection; coronary artery spasm; congestive heart failure; abnormally rapid heartbeat; cardiomyopathy, i.e., weakening of the cardiac muscle; and physical injuries or trauma to the heart due to vehicular accidents, etc.
  • Excessive stress on the heart caused due to prolonged periods of exercising such as triathlons or marathons can also elevate the levels of troponin protein complexes.
  • Some types of medical surgeries and therapies like electrical cardioversion or cardiac defibrillation, wherein the heart is given shocks to remedy anomalous cardiac rhythm;  open heart surgery; radiofrequency ablation therapy of the heart; and cardiac angioplasty or stenting.
  • Prolonged kidney disorders; pulmonary high blood pressure; and/or pulmonary embolism, i.e., obstructions in an artery of the lungs due to fat, blood clots, or tumor cells.

Troponin normal range

The levels of cardiac troponin are usually so low that they aren’t noticed in a majority of blood tests.

The presence of normal levels of troponin 12 hours after the patient has complained of chest pains means that the chances of a heart attack are minimal.

The troponin normal range may differ slightly from one lab to another. Some laboratories may test varied samples or use varied measurements. Additionally, some laboratories may have varying standard cut-off levels for probable and normal myocardial infarction. It is best to consult the health care provider to understand and interpret the results of a troponin test.

Troponin normal range: Reference cut-off points

  • For people who complain of heaviness and pain in the chest area, doctors will check for the levels of just TnT and TnI. Measurements of troponin T and troponin I levels after a cardiac arrest can help a doctor in determining the extent and severity of damage to the cardiac muscle. The test can is also very useful in ascertaining unstable angina or a cardiac arrest.
  • The reference range of TnT and TnI fall between 0 to 0.1 ng/mL (nanograms per milliliter of blood) and between 0 to 0.4 ng/mL, respectively.

Working mechanism of a troponin test

  • The levels of some substances in blood become higher after a heart attack. The substances are called cardiac biomarkers and include CK-MB/creatine kinase isoenzyme, troponin, myoglobin, and creatine kinase.
  • If they suspect an underlying case of a cardiac arrest, doctors will perform a troponin test many times over in the following 15 to 20 hours.
  • Raised troponin levels can be seen in less than 4 hours after any kind of injury to the heart muscle.
  • The troponin levels in people who have recently suffered from a heart attack tend to remain elevated for nearly 2 weeks. Thus a troponin test can be used by doctors to determine the best treatment option.

Elevated troponin levels act as a warning sign for cardiac problems in the future. Patients must therefore consult a doctor for suggestions, and make lifestyle changes, etc

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