Troponin test
Also known as: high-sensitivity troponin, cardiac troponin, troponin I, troponin T, cardiac enzymes
A blood test for cardiac troponin, a protein released when heart muscle cells are injured. It is the test that rules a heart attack in or out: with modern high-sensitivity assays, a value above the assay's upper limit and a rise or fall between two samples taken a few hours apart, read alongside the symptoms and the ECG, defines acute myocardial injury.
- Abbreviations
- hs-cTn, cTnI, cTnT
- Kind
- Laboratory test
- Categories
- Cardiovascular, Chemistry & metabolic
- Specimen
- Serum or plasma
- Method
- Immunoassay
- Terminology
- LOINC 10839-9, 6598-7
- Type
- Blood test
- Sample
- Blood from a vein, two samples a few hours apart
- Used for
- Suspected heart attack, heart muscle injury
- Measures
- Cardiac troponin I or T released from injured heart muscle
- Result
- Numeric, compared with the assay's 99th-percentile upper reference limit and with the previous sample
Why is it used?
- Chest pain or other symptoms of a possible heart attack (on arrival and again after 1-3 hours)
- Suspected myocarditis or pericarditis
- Assessing heart injury in pulmonary embolism, sepsis and critical illness
- After cardiac procedures, to detect procedure-related injury
- Risk stratification in acute coronary syndromes
What does it measure?
| Component | What it measures | A higher value may be seen in | A lower value may be seen in |
|---|---|---|---|
| Cardiac troponin hs-cTn High-sensitivity troponin | Cardiac troponin I or T in blood | Acute injury (rise or fall pattern) or chronic injury (stable level): infarction, myocarditis, heart failure, pulmonary embolism, sepsis, kidney disease | A low level is expected; it makes acute infarction unlikely when the timing is right |
A high or low value can be associated with several different situations; the result is interpreted with other results, symptoms, history and clinical findings.
How is it performed?
A venous blood sample; a second sample is timed from symptom onset or from arrival so that a rise or fall can be seen. Results are usually available within an hour in emergency departments.
Specimen. Venous blood (serum or plasma)
Do I need to prepare?
None.
What do the results generally mean?
| Finding | What it may indicate |
|---|---|
| Troponin above the assay's 99th percentile with a rise or fall between samples | Acute myocardial injury; with symptoms of ischaemia, ECG change or imaging evidence it is classified as a myocardial infarction |
| Chronically raised, flat troponin on repeat samples | Injury without an acute event: chronic kidney disease, heart failure, structural heart disease, older age |
| Very low or undetectable troponin hours after symptom onset | Acute infarction is very unlikely; other causes of the symptoms are considered |
| Raised troponin with a clear non-cardiac illness | Pulmonary embolism, sepsis, kidney failure, a very fast rhythm or extreme exertion can all release troponin |
Guideline thresholds
| Threshold | Value | Unit | Applies to | Country · source |
|---|---|---|---|---|
| Myocardial injury | above the assay's 99th percentile upper reference limit | ng/L (assay-specific) | Acute injury requires a rise and/or fall on serial samples; with evidence of ischaemia it is a myocardial infarction | UK UK |
Clinical decision thresholds come from the named guideline and country; they are not laboratory reference intervals, and they change when guidance changes.
What can affect the result?
- Time since symptom onset: sampling too early can miss the rise
- Kidney function, which slows clearance
- The assay used and its sex-specific limits
- Very rarely, interfering antibodies in the sample
- Recent strenuous exercise, cardioversion or cardiac procedures
Medicines. Few medicines change troponin directly; cardiotoxic chemotherapy and some drugs that cause myocarditis can raise it.
What can the test not tell you?
- Whether the injury was caused by a blocked coronary artery or by something else
- Whether the heart's pumping function is reduced (that needs an echocardiogram)
- Whether chest pain that started minutes ago is a heart attack, until the second sample
Troponin says that heart muscle was injured, not why: many conditions other than a blocked coronary artery raise it. A single sample taken too early can be normal, so the timing of the second sample matters. Each assay has its own reference limit, and results from different hospitals are not directly comparable.