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Cohort study High-sensitivity troponin useful for diagnosis and prognosis in patients with acute coronary syndrome Eugenio Stabile, Alessia Agresta Context 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 CAD. 1 2 Some studies have shown higher specificity of hs-cTnT in AMI diagnosis, compared with common cTnT determinations. 3 Hs-cTnT is also a better predictor of death and heart failure in patients with chest pain and ACS during follow-up. 124 Methods The APACE study, a multicentre prospective trial, enrolled a total of 1181 consecutive patients who were admitted to the emergency department because of chest pain and/or other symptoms suggestive of AMI for less than 12 h duration. Patients who presented with symptoms that lasted for more than 12 h or with renal failure requiring dialysis were excluded. Patients underwent hs-cTnT determination at presen- tation, and within 3 h, unless the diagnosis of AMI was certain. The 99th percentile of hs-cTnT was the cut-off point, with a coefficient of variation <10% (achieved at 0.013 ug/l). Samples were assayed in a blinded fashion. Final diagnosis of ACS was obtained by two independ- ent cardiologists (the authors did not provide a measure of agreement between the cardiologists). Clinical follow-up was done 30, 90 and 360 days after hospital discharge. The primary endpoint was death from all causes. Findings A total of 351 patients had ACS during hospitalisation. Of these, 187 (53%) had AMI and 164 (47%) had unstable angina (UA). Hs-cTnT was below the 99th percentile in 112 patients (31.9%, 11 of whom had AMI, 5.9%) and above the 99th percentile in 239 patients (68.1%). In the 9/11 AMI patients with follow-up hs-cTnT at 3 h, all of them were positive, with 7/67 patients with UA with follow-up hs-cTnT becoming positive. During follow-up, mortality from all causes was higher in patients with ACS and elevated hs-cTnT versus those with ACS and normal hs-cTnT (7.5% vs 0% at 30 days, p=0.003; 10.8% vs 0% at 90 days, p<0.001; 17.5% vs 2.0% at 360 days, p<0.001). Patients with ACS and normal hs-cTnT had an increased AMI rate at the 360-day follow-up (15% vs 5.4%; p=0.004) but a low- death rate, similar to patients with non-cardiac chest pain, indicating high-cardiovascular risk. Due to the hs-cTnT determination, Meune et al were able to diagnose an AMI in 94% of cases at admission and in 100% of the cases, if the assay was repeated at 3 h. Commentary These data support that the hs-cTnT is useful for diagnosis and prognosis of patients with ACS. 1–4 There is a physiologic continuum between 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. We speculate that hs-cTnT determination to diagnose AMI, will improve patient outcomes by leading to earlier AMI treatment. Due to the high sensitivity of hs-cTnT test, however, physicians should be wary of interpretation to avoid AMI misdiagnosis in patients with minimal cTnT increases, which are common in patients affected by other diseases. 4 Patients with ACS and normal hs-cTnT, and a higher AMI rate at 360-day follow-up, were younger and already on statins, aspirin and clopidogrel treatment, with normal renal function. This reflects that these patients had a higher baseline risk. Physicians should always be wary of ACS, even if circulating troponin is normal at onset. Careful follow-up for risk factor modification is important. References 1. Aldous SJ, Richards M, Cullen L, et al. Diagnostic and prognostic utility of early measurement with high-sensitivity troponin T assay in patients presenting with chest pain. CMAJ 2012; CMAJ. 2012 Mar 20;184(5):E260–8. Epub 2012 Jan 30. 2. Reiter M, Twerenbold R, Reichlin T, et al. Early diagnosis of acute myocardial infarction in patients with pre-existing coronary artery disease using more sensitive cardiac troponin assays. Eur Heart J 2012;33:988–97. 3. Aldous SJ, Florkowski CM, Crozier IG, et al. The performance of high sensitivity troponin for the diagnosis of acute myocardial infarction is underestimated. Clin Chem Lab Med 2011;50:727–9. 4. Mills NL, Lee KK, McAllister DA, et al. Implications of lowering threshold of plasma troponin concentration in diagnosis of myocardial infarction: cohort study. BMJ 2012;344:e1533. 10.1136/ebmed-2012-100792 Department of Cardiology, Centro Polidiagnostico Stabile, Salerno, Italy Correspondence to: Eugenio Stabile Department of Cardiology, Centro Polidiagnostico Stabile, via diaz 32, Salerno 84100, Italy; [email protected] 42 Evidence-Based Medicine February 2013 | volume 18 | number 1 | Diagnosis

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