Also known as:TnI; TnT; cTnI; cTnT
Formal name:Cardiac-specific Troponin I and Troponin T
Related tests:CK; CK-MB; Myoglobin; Cardiac Biomarkers
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Why Get Tested?
To determine if you have had a heart attack or injury to heart muscle; to determine if your angina (chest pain related to heart trouble) is worsening
When to Get Tested?
Immediately, then followed by a series of troponin tests over several hours when you are having signs and symptoms that may be due to a heart attack, such as pain in your chest, shoulders, neck, jaw and/or shortness of breath; when your angina worsens, especially if it does not resolve with rest
A blood sample drawn from a vein in your arm
Test Preparation Needed?
How is it used?
Troponin tests are primarily ordered to help diagnose a heart attack and rule out other conditions with similar signs and symptoms. Either a troponin I or troponin T test can be performed; usually a laboratory will offer one test or the other. The concentrations are different, but they basically provide the same information.
Troponin I and troponin T are proteins found in heart muscle and are released into the blood when there is damage to the heart.
Troponin tests are also sometimes used to evaluate people for heart injury due to causes other than a heart attack or to distinguish signs and symptoms such as chest pain that may be due to other causes. Testing may also be done to evaluate people with angina if their signs and symptoms worsen.
Troponin tests are sometimes ordered along with other Cardiac Biomarkers, such as CK-MB or Myoglobin. However, troponin is the preferred test for a suspected heart attack because it is more specific for heart injury than other tests (which may be elevated in the blood with skeletal muscle injury) and remain elevated for a longer period of time.
A test called high-sensitivity troponin detects the same protein that the standard test does, just at much lower levels. Because this version of the test is more sensitive, it becomes positive sooner and may help detect heart injury and acute coronary syndrome earlier than the standard test. The hs-troponin test may also be positive in people with stable angina and even in people with no symptoms. When it is elevated in these individuals, it indicates an increased risk of future heart events such as heart attacks. Currently, this test is not approved in the U.S., but research is ongoing and it may become available in the near future. It is already routinely used as a cardiac biomarker in clinical practice in Europe, Canada, and other countries as well.
When is it ordered?
A troponin test will usually be ordered when a person with a suspected heart attack first comes into the emergency room, followed by a series of troponin tests performed over several hours.
A heart attack may be suspected and testing done when a person has signs and symptoms such as those listed below. Note that not everyone will experience chest pain, and women are more likely than men to have sign and symptoms that are not typical.
- Chest pain, discomfort and/or pressure (most common)
- Rapid heart rate, skipping a beat
- Shortness of breath and/or difficulty breathing
- Nausea, vomiting
- Cold sweat
- Undue fatigue
- Pain in other places: back, arm, jaw, neck, or stomach
In people with stable angina, a troponin test may be ordered when:
- Symptoms worsen
- Symptoms occur when a person is at rest
- Symptoms are no longer eased with treatment
These are all signs that the angina is becoming unstable, which increases the risk of a heart attack or other serious heart problem in the near future.
What does the test result mean?
A high troponin and even slight elevations may indicate some degree of damage to the heart. When a person has significantly elevated troponin levels and, in particular, a rise in the results from a series of tests done over several hours, then it is likely that the person has had a heart attack or some other form of damage to the heart. Levels of troponin can become elevated in the blood within 3 or 4 hours after heart injury and may remain elevated for 10 to 14 days.
In people with angina, an elevated troponin may indicate that their condition is worsening and they are at increased risk of a heart attack.
Troponin levels may also be elevated with other heart conditions such as myocarditis (heart inflammation), weakening of the heart (cardiomyopathy), or congestive heart failure, and with conditions unrelated to the heart, such as severe infections and kidney disease.
Normal troponin values in a series of measurements over several hours means that it is unlikely that a person's heart has been injured. Signs and symptoms may be due to a cause unrelated to the heart.
Because troponin tests are measuring cardiac muscle-specific troponin, the test is not affected by damage to skeletal muscles, so injections, accidents, and drugs that can damage muscle do not affect cardiac troponin levels. Troponin may rise following strenuous exercise, although in the absence of signs and symptoms of heart disease, it is usually of no medical significance.
Is there anything else I should know?
Increased troponin levels should not be used by themselves to diagnose or rule out a heart attack. A physical exam, clinical history, and ECG are also important. Your healthcare provider may also need to see whether the troponin levels from a series of tests are stably elevated or show a rise over several hours.
Very rarely, people who have a heart attack will have normal troponin concentrations, and some people with increased troponin concentrations have no apparent heart injury.
What is being tested?
Troponins are a family of proteins found in skeletal and heart (cardiac) muscle fibers that produce muscular contraction. Troponin tests measure the level of cardiac-specific troponin in the blood to help detect heart injury.
There are three types of troponin proteins: troponin C, troponin T, and troponin I. Troponin C initiates contraction by binding calcium and moves troponin I so that the two proteins that pull the muscle fiber shorter can interact. Troponin T anchors the troponin complex to the muscle fiber structure. There is little or no difference in troponin C between skeletal and cardiac muscle, but the forms of troponin I and troponin T are different. Measuring the amount of cardiac-specific troponin T or troponin I in the blood can help identify individuals who have experienced damage to their heart.
Normally, troponin is present in very small to undetectable quantities in the blood. When there is damage to heart muscle cells, troponin is released into the blood. The more damage there is, the greater the concentration in the blood. Primarily, troponin tests are used to help determine if an individual has suffered a heart attack. They may also be helpful in evaluating someone for other forms of heart injury.
When a person has a heart attack, levels of cardiac-specific troponins I and T can become elevated in the blood within 3 or 4 hours after injury and may remain elevated for 10 to 14 days.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
- What does heart attack mean?
Heart attack means that some of the muscle tissue in your heart is severely injured or has died. The medical term for the death of cardiac muscle is myocardial infarction. Because it is not always possible to determine whether there is only serious injury or there is infarction, the general term for the condition is acute coronary syndrome (ACS).
Most commonly, a heart attack starts with a sensation of heavy pressure or pain in the chest, often extending into the neck or left arm. You may have trouble catching your breath or you may feel weak and break into a cold sweat. Read about what a heart attack feels like on the National Heart, Lung, and Blood Institute web site.
A heart attack usually occurs because one of the blood vessels (called coronary arteries) that bring blood to your heart muscle is blocked. This usually happens when a blood clot forms in a blood vessel that is already partially closed. The partial closure is usually due to atherosclerosis (often called hardening of the arteries). Obstruction occurs gradually over many years as lipid plaques are deposited along the walls of the blood vessels. These plaques narrow and stiffen the arteries and can rupture unexpectedly, totally blocking off the affected artery.
- If I have chest pain, does that mean I am having a heart attack?
Many other problems can cause chest pain, and it is not possible to tell from the type of chest pain whether or not you are having a Heart attack. Many people have chest pain from straining the muscles in their chest, from heartburn or other problems involving the stomach and esophagus, from emotional stress, and with some lung problems. Chest pain that occurs during exercise, hard work, or at times of stress, lasts for a few minutes, and goes away with rest is often caused by angina. A relatively rare form of chest pain may be due to temporary heart spasms called variant angina. These spasms usually occur at night when a person is resting and can cause severe but temporary pain.
If chest pain lasts longer than just a few minutes, especially if it occurs when you are resting, seek immediate medical attention.
- What if I am not sure if I am having a heart attack?
Many people are not sure if they are experiencing a Heart attack. If you are unsure, don't wait, but get help. If you have ongoing pain in the upper body such as the chest, shoulders, arms, neck or jaw or pain in the upper part of your stomach, or if you have been previously diagnosed with angina and the drugs you were prescribed do not ease the pain, seek immediate medical attention. Shortness of breath, nausea, sweating and dizziness are also signs and symptoms. Getting help right away can help you survive and treatments given soon after a heart attack can help limit the damage to your heart.
- What are high-sensitivity troponin (hs-troponin) tests?
High-sensitivity troponin tests measure the same protein in the blood as the standard test but at much lower levels. Because these new generation of tests are more sensitive than standard ones, they become positive sooner and may help detect acute coronary syndrome earlier. The hs-troponin test may also be positive in people with stable angina and even in people with no symptoms. In these cases, a positive test indicates an increased risk of future heart events such as heart attacks. Hs-troponin is not approved in the U.S. at this time, but research is ongoing and it may become available soon. It is already routinely used in Europe, Canada, and other countries as well.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.