High sensitivity troponin T guideline
Acute coronary syndromes incorporate two conditions:
- Unstable angina, and
- Acute myocardial infarction (AMI), which is further
- ST elevation myocardial infarction (STEMI), which can be
diagnosed using an ECG, and
- Non-ST elevation myocardial infarction (NSTEMI), which can
only be reliably diagnosed using cardiac biomarkers
Cardiac troponin is the biomarker of choice for diagnosing or
excluding acute myocardial infarction (AMI).
CMFT currently uses the high sensitivity troponin T assay from
Roche Diagnostics (hs-cTnT).
In patients whose symptoms and/or signs lead treating clinicians
to suspect a diagnosis of acute coronary syndrome, hs-cTnT should
be measured at the time of admission or as soon as possible
following the onset of symptoms.The test should be repeated 12
hours after the onset of the peak symptoms.
The lowest reportable level of hs-cTnT is 3ng/L (the 'limit of
blank' or LoB)
The 'normal range' of hs-cTnT is <14n/gL (the 99th percentile
in apparently healthy individuals)
Levels between the limit of blank (3ng/) and 14ng/L are normal
and will be detected in more than half of apparently healthy
If any patient has a hs-cTnT level >14ng/L they should have a
second sample sent for hs-cTnT testing six hours later.
Haemolysis can cause a falsely low level of hs-cTnT
AMI must not be 'ruled out' using a haemolysed sample
Haemolysed samples cannot be used to quantify the rise and/or
fall of hs-cTnT on serial testing (the 'delta troponin').
A positive hs-cTnT (>14ng/L) may still be used to risk
stratify patients, even in the presence of haemolysis. However, the
sample should still be repeated immediately in order to allow
quantification of the rise and/or fall.
To 'rule out' AMI
In patients who present to hospital >12 hours after the onset
of peak symptoms, a single hs-cTnT level <14ng/L can be used to
rule out AMI. However: the clinician should be certain that the
peak symptoms occurred >12 hours ago. If there is any doubt,
repeat the test 12 hours after the latest symptoms.
In patients who present to hospital <12 hours after the onset
of peak symptoms, or whose symptoms occur while in hospital: AMI
can be ruled out if both hs-cTnT levels are <14ng/L
Patients with hs-cTnT levels >14ng/L may still have AMI 'ruled
out' if they do not demonstrate a significant rise and/or fall
(delta troponin) on serial testing (see below). 'Ruling out' AMI in
these circumstances is a clinical decision and must be based on the
clinical context, putting together all of the relevant clinical
information for the individual patient. Review by a senior
clinician with expertise in this area is recommended. In order to
'rule out' a rise and/or fall of hs-cTnT, serial samples should be
taken six hours apart.
In patients who present for medical attention very late
(>72h) after symptom onset, hs-cTnT levels may have returned to
baseline, precluding the detection of a rise and/or fall of
hs-cTnT. If there is ongoing suspicion of late-presenting AMI,
additional investigation is recommended.
To 'rule in' AMI
Hs-cTnT cannot 'rule in' AMI. The result must be interpreted in
the clinical context. A diagnosis of AMI can be established in the
A rise and/or fall of hs-cTnT to above 14ng/L in conjunction
with at least one of:
- Symptoms of myocardial ischaemia
- New or presumed new ST-segment-T wave changes or new left
bundle branch block in the ECG
- Development of pathological Q waves in the ECG
- Imaging evidence of new loss of viable myocardium or new
regional wall motion abnormality
- Identification of an intracoronary thrombus by angiography or