Troponin test explained (hs-TnI/TnT)

Troponin is a protein found inside heart muscle cells that takes part in muscle contraction. In the blood of a healthy person there is almost none of it, but when the heart muscle is damaged (for example during a myocardial infarction) troponin is released into the blood and its concentration rises within a few hours. Two forms are used in laboratory diagnostics — troponin I (TnI) and troponin T (TnT); modern, sensitive (hs — high-sensitivity) tests make it possible to detect even small damage to the heart muscle. According to MedlinePlus, a troponin test is most often done when a heart attack is suspected, and the result is assessed not as a one-off number but as a change over time — by repeating the test after a few hours, because after damage the concentration rises and later falls along a characteristic time course. Troponin can also rise because of other cardiac or non-cardiac causes, so the result is always interpreted by a doctor together with symptoms, an ECG and other tests.

• When there is chest pain or pressure spreading to the arm, back, shoulder or jaw — when a heart attack is suspected
• When breathlessness, unusual tiredness, dizziness, heavy sweating or nausea appear together with chest discomfort
• When the heartbeat feels fast or irregular (arrhythmia)
• When diagnosing and monitoring unstable angina
• After heart surgery or a procedure — to check whether the heart muscle has been damaged
• When assessing other possible causes of heart muscle damage, together with other cardiac markers

Troponin reference limits depend on the laboratory and on the test method (hs-TnI or hs-TnT), so you will find the exact limit on your own result sheet. The upper limit is set at the 99th percentile of healthy people: the Danish physicians' handbook Lægehåndbogen, for example, gives below 14 ng/l for troponin T and 25–45 ng/l for troponin I, depending on the method. According to MedlinePlus, a normal troponin level 12 hours after chest pain began indicates that a heart attack is unlikely.

A raised troponin

A raised troponin most often indicates damage to the heart muscle and is the main marker when a heart attack is suspected. However, troponin can also rise because of other conditions — heart failure, valve disease, myocarditis, pulmonary embolism, a severe infection or an arrhythmia — so the result is always assessed by a doctor together with symptoms and other tests.

What can raise troponin

• Myocardial infarction (heart attack) — the most common cause
• Unstable angina and other damage to the heart muscle
• A fast or irregular heartbeat (arrhythmia)
• Pulmonary hypertension and pulmonary embolism
• Heart failure
• Myocarditis (inflammation of the heart muscle)
• Long-lasting intense physical exertion
• Chest injury
• Heart surgery
• Kidney disease
• A severe infection (sepsis) or a severe COVID-19 infection
• Aortic dissection, amyloidosis and medicines that are toxic to the heart (according to the Danish physicians' handbook Lægehåndbogen)

Symptoms that can occur alongside

• Chest discomfort or pain
• Pain in the arm, back, shoulder or jaw
• Difficulty breathing
• Nausea
• Unusual tiredness
• Dizziness
• Heavy sweating
• A fast or irregular heartbeat (arrhythmia)

What to discuss with a doctor

• Whether chest pain, breathlessness or other symptoms were present at the same time — this determines how urgent the test is
• A repeat test after a few hours — the amount of troponin changes over time after damage
• An ECG and other heart tests, which help to establish the cause of the damage
• Whether a heart procedure or operation has been carried out recently
• Kidney function — kidney disease can affect the amount of troponin in the blood

What a single result does not tell you

A troponin result on its own is not a diagnosis. The amount in blood rises and later falls along a characteristic time course after damage to the heart muscle, so a one-off result is not always informative, and the test is often repeated after a few hours to see the change. The result is always interpreted by a doctor together with symptoms, an ECG and other tests. On reading laboratory results in general, see how to read blood test results.