High sensitivity cardiac troponins (hs - cTnT)

• High-sensitivity cardiac troponin (hs-cTnT) determination has improved cTnT evaluation in patients with acute coronary syndrome (ACS)
  • the hs-cTnT 'normal value' is considered to be <99th percentile (0.014 ug/l)
  • Hs-cTnT can diagnose an acute myocardial infarction (AMI) earlier than common cTnT determinations, even in patients with previous coronary artery disease
    • sensitivity of the assay at presentation was 100% among patients who presented four to six hours after symptom onset
  • there is study evidence of higher specificity of hs-cTnT in AMI diagnosis, compared with common cTnT determinations
  • Hs-cTnT is also a better predictor of death and heart failure in patients with chest pain and ACS during follow-up than common cTnT
• there is a physiologic continuum between unstable angina (UA) and AMI and the hs-cTnT appears to be useful for the early diagnosis of AMI; serial measurements support the concept of a continuum

NICE state that (2):

• optimum sensitivity of non-high-sensitivity troponin assays for acute MI occurs 10-12 hours after the onset of symptoms. For many people, this results in the need for hospital admission and observation while serial troponin testing is carried out
  
  
• high-sensitivity troponin assays have been developed - able to detect lower levels of troponin in the blood earlier than older standard assays, leading to improved early detection of acute MI
  • allows non-ST -segment elevation myocardial infarction (NSTEMI) to be ruled out within 4 hours, if test results are available within 3 hours of presentation to the emergency department
  • increased sensitivity of these assays could mean a shorter inpatient hospital stay for people without raised levels of troponin and earlier intervention for those with a confirmed NSTEMI
  • as with older standard troponin assays, the high-sensitivity assays are intended to be used with clinical history taking and the electrocardiogram to diagnose NSTEMI because, despite being highly specific for cardiomyocyte necrosis, troponin may also be raised in people who do not have underlying evidence of ischaemic heart disease
  • conditions other than acute MI that may cause troponin levels to be raised include myocarditis, congestive heart failure, severe infections, musculoskeletal conditions and renal disease

Reference:

• 1) Aldous SJ et al. Diagnostic and prognostic utility of early measurement with high-sensitivity troponin T assay in patients presenting with chest pain.CMAJ. 2012 Mar 20;184(5):E260-8
• 2) NICE (October 2014).Myocardial infarction (acute): Early rule out using high-sensitivity troponin tests (Elecsys Troponin T high-sensitive, ARCHITECT STAT High Sensitive Troponin-I and AccuTnI+3 assays).