What is the normal range for troponin levels?
The heart releases troponin into the blood following an injury, such as a heart attack. Very high troponin levels usually mean that a person has recently had a heart attack. The medical term for this attack is myocardial infarction.
In this article, we discuss what troponin is, why doctors test troponin levels, and what the normal range is. We also cover the causes and treatment of high troponin levels and what to expect during the test.
What is troponin?
A doctor may test troponin levels if a person is experiencing possible symptoms of a heart attack.
Troponin refers to three different proteins. Troponin C binds calcium and transports troponin I so that muscles can contract. Troponin T binds troponin proteins to muscle fibers.
The heart is essentially a muscle, and damage to the heart causes it to release troponin into the bloodstream. Troponin levels in the blood are normally very low, but injuries to the heart can cause the levels to increase significantly.
Troponin tests typically measure levels of troponin I or troponin T in the blood as a way to check for heart damage.
Why do doctors test troponin levels?
A troponin test can help detect an injury to the heart. A doctor may order the test if a person is experiencing possible symptoms of a heart attack, such as:
- chest pain
- shortness of breath
- a rapid heart rate
A doctor will not use elevated troponin levels alone to diagnose a heart condition. They will also take into account the person's other symptoms and may use other diagnostic tools, such as a physical examination or an electrocardiogram (ECG).
Troponin testing, however, allows a doctor to assess the extent of any heart damage, which can guide treatment decisions and help determine if current treatments are effective.
What is the normal troponin range?
Troponin levels are usually so low that standard blood tests are unable to detect them. Even small increases in troponin can indicate some damage to the heart.
Significantly raised levels of troponin, particularly if they rise and fall over a series of hours, are a strong indication of a heart injury.
The range for normal troponin levels can vary between laboratories, so it is best to discuss the results with the doctor who ordered the test. Laboratories measure troponin in nanograms per milliliter of blood (ng/ml).
The University of Washington's Department of Laboratory Medicine provides the following ranges for troponin I levels:
- Normal range: below 0.04 ng/ml
- Probable heart attack: above 0.40 ng/ml
Having a result between 0.04 and 0.39 ng/ml often indicates a problem with the heart. However, a very small number of healthy people have higher than average levels of troponin. So, if the result is in this range, a doctor may check for other symptoms and order further tests before making a diagnosis.
According to Lab Tests Online, many labs in the United States are now using a high-sensitivity version of the troponin test, which the Food and Drug Administration (FDA) approved in 2017. This newer test can detect elevated troponin levels earlier than previous versions.
Doctors usually order a series of troponin tests to monitor how a person's levels are changing over time.
Causes of high troponin levels
Elevated troponin levels may result from sepsis, kidney failure, heart failure, or a traumatic injury to the heart.
Very high levels of troponin typically indicate that a person has had a heart attack, which can occur if the blood supply to some of the heart muscle suddenly becomes blocked.
Lower but elevated troponin levels may point to another diagnosis.
Some causes of elevated troponin levels can include:
- sepsis, which is a severe and potentially life-threatening reaction to an infection entering the bloodstream
- kidney failure or chronic kidney disease
- heart failure
- chemotherapy-related damage to the heart
- pulmonary embolism
- heart infection
- myocarditis, which is inflammation of the heart
- heart damage from using recreational drugs, such as cocaine
- a traumatic injury to the heart, such as from a sudden, hard blow to the chest
Treatment for high troponin levels
High troponin levels are a symptom, not a diagnosis, so treatment will focus on finding and addressing the underlying cause.
Very high levels of troponin usually indicate that a person has recently had a heart attack. Treatment for a heart attack depends on whether the blockage preventing blood flow to the heart is partial or complete.
Some common treatments of a heart attack include:
- clot-dissolving medications
- coronary angioplasty, which is a procedure that involves threading a small balloon into the coronary artery to open up the blockage
- the insertion of a stent — a wire mesh tube — to prop open a blocked blood vessel during an angioplasty
- bypass surgery, which involves a surgeon creating new pathways for blood to travel to the heart muscle
- ablation, which is a treatment that destroys certain heart cells using radio waves
To prevent the risk of further heart attacks, a doctor will usually recommend lifestyle changes, such as quitting smoking, losing weight, getting more exercise, and eating a more healthful diet.
Treatments of other causes of high troponin levels may be different from treatments of a heart attack.
What happens during the test?
A troponin test is a simple blood test, and a healthcare professional will usually take the blood sample from the arm. Blood tests are generally very safe and quick.
To take the blood sample, the healthcare professional usually begins by wrapping a band around the person's upper arm. Tightening this band causes the blood vessels to swell, making it easier to draw the blood.
The healthcare professional will then insert a needle into a blood vessel and withdraw some blood. The needle may cause a short, sharp sensation, but many people feel little or no pain.
It is important for a person to inform the healthcare professional if they feel dizzy or nauseous after giving the sample. Sitting for 5–10 minutes and drinking a glass of water or sugary juice can help relieve dizziness and nausea.
A doctor may request additional blood samples over the course of a few hours.
Doctors use troponin tests to assess whether there is damage to a person's heart. Very high levels of troponin can indicate a recent heart attack.
Doctors usually order troponin testing if they suspect that a person has had a recent heart attack. Higher than normal levels of troponin can also indicate other injuries and conditions that affect the heart.
However, doctors do not use elevated troponin levels alone to diagnose a heart condition. They will also take into account the person's other symptoms and may order further tests, such as an ECG.
Treatment for high troponin levels depends on the underlying cause. For people having a heart attack, treatment may involve emergency procedures to open the blocked artery.