High Sensitivity Troponin T (Blood)

Diagnostic Use

A raised troponin T level indicates myocardial damage, of which there are many causes. The reference range is based on the 99th centile found in a healthy group of subjects.

Myocardial infarction:

An elevated troponin is not specific for myocardial infarction.

Therefore it is crucial to use the test in a way that maximises clinical specificity  for myocardial infarction. The first principle is that the test should be ordered only in clinical circumstances which are consistent with acute myocardial ischaemia.

To fulfil the definition for diagnosis of myocardial infarction there must be a change in hsTnT demonstrated over time.   Infarction cannot be ruled out until a negative troponin is obtained at 9-12 hours after onset of symptoms.

To avoid over-interpretation of changes which may reflect only normal biological and analytical variability, the following criteria are suggested:

• Between 15 and 50 ng/L the change should be at least 50%. 
• At levels above 50 ng/L the change should be at least 20%.

Troponin T levels may remain elevated for up to 10 days after MI.

 

Conditions other than coronary artery disease which can caused elevated troponin:

• myocarditis, cardiomyopathy, drug toxicity (e.g. chemotherapy)
• demand ischaemia (myocardial ischaemia not due to coronary artery disease):  septic shock, hypotension, hypovolaemia, SVT/atrial fibrillation, LV hypertrophy.
• myocardial strain: cardiac failure, pulmonary embolism, pulmonary hypertension
• cardiac trauma, contusion or cardioversion
• renal failure: troponins are frequently persistently elevated in patients with end-stage renal disease.  Decreased clearance may partly explain this, but other factors (e.g. clinically silent myocardial necrosis) have also been proposed.  However, elevated troponin is associated with a worse prognosis across the whole spectrum of renal failure.
• Skeletal Muscle disorders e.g.  polymyositis and Duchenne muscular dystrophy.  Skeletal muscle troponin is not detected by the troponin T assay; a raised level indicates myocardial involvement.
• Assay interferences: Very rarely, heterophile antibodies or other causes may result in a falsely elevated result.  If in doubt troponin I can be tested in another laboratory. CK may be useful to confirm myocardial damage.

Reference Intervals