Troponin levels and odds of MI or death
A prospective study of 1852 patients with suspected ACS from 3 trial populations evaluated the prognostic value of increased troponin levels vs CK-MB levels at initial presentation, compared with a reference group with normal troponin and CK-MB levels.3 Patients with isolated troponin elevation had an increased odds of MI or death at 24 hours (odds ratio [OR]=5.2; 95% confidence interval [CI], 2.2-11.9) and 30 days (OR=2.1; 95% CI, 1.4-3.0), whereas patients with isolated CK-MB elevations didn't. At 30 days, patients with isolated CK-MB elevations equaled the reference group odds for MI and death (OR=1.0; 95% CI, 0.6-1.6).
Serial troponin assessment boosts diagnostic sensitivity
A prospective cohort study found that serial measurements of troponin increased the diagnostic sensitivity for AMI.4 Investigators evaluated 1818 consecutive patients with new onset chest pain in 3 German chest-pain units with troponin levels on admission and at 3 and 6 hours later. The gold standard was diagnosis of AMI by 2 independent cardiologists. Troponin measurement produced an AUC of 0.96 at admission, increasing to 0.98 and 0.99 at 3 and 6 hours after admission, respectively.
RECOMMENDATIONS
The American College of Cardiology and American Heart Association recommend measuring biomarkers of cardiac injury in all patients who present with chest discomfort consistent with ACS.5 A cardiac-specific troponin is the preferred marker and should be measured in all patients. If troponin is not available, CK-MB is the best alternative. Cardiac biomarkers should be repeated 6 to 9 hours after presentation and, in patients with a high clinical suspicion of AMI, at 12 to 24 hours.6,7