Biomarker · Heart

Cardiac troponin

Also known as: troponin I, troponin T, hs-troponin, high-sensitivity troponin, cTnI, cTnT

A protein of the contractile apparatus of heart muscle cells that leaks into blood when those cells are injured. High-sensitivity troponin is the blood marker that rules a heart attack in or out, read as a change between two samples a few hours apart.

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Also known as
troponin I, troponin T, hs-troponin, high-sensitivity troponin, cTnI, cTnT
Units
ng/L; every assay has its own 99th-percentile upper reference limit, so numbers are not comparable between hospitals
Measured by
Troponin test, Electrocardiogram, Echocardiogram

What it is and what it does

Troponin I and troponin T are parts of the machinery that lets calcium trigger contraction in heart muscle; the cardiac forms are distinct from those in skeletal muscle, so the assay is specific to the heart. When cardiac cells die, troponin appears in blood within a few hours, peaks around a day and can stay raised for one to two weeks. Modern high-sensitivity assays detect tiny amounts in almost everyone, so the diagnosis of acute injury rests on a value above the assay's 99th percentile together with a rise or fall between serial samples, interpreted with symptoms and the ECG. Injury is not the same as infarction: pulmonary embolism, sepsis, myocarditis, kidney failure, very fast heart rhythms and extreme exertion all release troponin without a blocked coronary artery.

Why it may be higher

  • Acute myocardial infarction (with a rise or fall on serial samples)
  • Myocarditis, pericarditis, heart failure, takotsubo cardiomyopathy
  • Pulmonary embolism, sepsis, severe respiratory failure
  • Tachyarrhythmias, cardiac procedures, cardioversion, chest trauma
  • Chronic kidney disease (reduced clearance) and structural heart disease (stable, flat elevation)

Why it may be lower

  • A low value is expected; an undetectable high-sensitivity result on arrival, hours after symptom onset, makes acute infarction very unlikely

A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.

What can affect the result

  • Time since symptom onset: a single early sample can be normal before the rise
  • Kidney function
  • Assay type and its 99th percentile; laboratory-specific sex-specific limits
  • Very rarely, antibodies in the sample interfere with the assay
Reference ranges. Reference intervals for this marker depend on the laboratory, the assay, the units, age, sex and pregnancy. Interpret a result against the interval printed on the laboratory report, not against a figure from the internet.
Educational content. A biomarker page explains what a substance is and why its level can change. It cannot determine the cause of your result: interpret a result using the range supplied by the laboratory that performed the test, with the clinician who ordered it.