Delta CK-MR outperforms delta troponin I at 2 hours during the ED rule out of acute myocardial infarction

It has been shown that a rise in creatine kinase MB bank (CK-MB) of greater than or equal to + 1.6 ng/mL in 2 hours is more sensitive and equally specific for detection of acute myocardial infarction (AMI) as compared with a 2-hour CK-MB greater than or equal to 6 ng/mL during the emergency department (ED) evaluation of chest pain. Because cardiac specific troponin I (cTnI) is thought to have similar early release kinetics as compared with CK-MB mass, we undertook a retrospective cohort study in 578 chest pain patients whose baseline CK-MB and cTnI was less than two times the hospital's upper limits of normal and who underwent a 2-hour CK-MB and cTnI to compare sensitivities and specificities of the 2-hour delta CK-MB (Delta CK-MB) and delta cTnI (Delta cTnI) for AMI and 30-day Adverse Outcome (AO), Thirty day AO was defined as AMI, life-threatening complication, death, or percutaneous transluminal coronary angioplasty (PTCA)/coronary artery bypass graft (CABG) within 30 days of ED presentation. Optimum delta values were determined by choosing the smallest cutoff value greater than the assay precision where the Delta CK-MB and Delta cTnI had a positive likelihood ratio for 30-day AO of greater than or equal to 15. A greater than or equal to CK-MB greater than or equal to + 1.5 ng/mL was more sensitive than a Delta TnI greater than or equal to +0.2 ng/mL for AMI (87.7% versus 61.4%; P < .0005) and 30-day AO (56.7% versus 42.3%; P <,005). There were no differences in specificities for AMI and 30-day AO, Combining the two tests (MBP greater than or equal to +1.5 ng/mL and/or a Delta TnI greater than or equal to +0.2 ng/mL) resulted in an incremental increase in sensitivity of 89.5% for AMI and 61.9% for AO (P <,005), Patients with either a rise in CK-MB of greater than or equal to +1.5 ng/mL or rise in cTnI of greater than or equal to +0.2 ng/mL in 2 hours should receive consideration for aggressive antiischemic therapy and further diagnostic testing before making an exclusionary diagnosis of nonischemic chest pain. Copyright (C) 2000 by W.B. Saunders Company.