Before troponins were used in cardiac disease diagnosis, CK-MB, an isoenzyme of creatine kinase (CK), was the marker of choice for AMI diagnosis. Despite its rapid decline in use, some laboratories still offer CK-MB testing.
CK-MB is released in the circulation 4 – 6 hours after symptoms of an AMI and usually peaks within 24 hours. Levels of CK-MB return to normal in about 48 – 72 hours. This timeframe differs from that of troponin, which stays elevated longer.
CK-MB results do not predict future adverse cardiac events and do not have any prognostic or risk stratification use.
In 2021, the AHA/ACC released a new guideline stating: "Comparative studies have confirmed the superiority of cTn over CK-MB and myoglobin for diagnosis and prognosis of AMI. The addition of CK-MB or myoglobin to cTn for evaluation of patients presenting with chest pain is not beneficial." Routine CK-MB testing is no longer recommended.2
2. Gulati, M, Levy, P, Mukherjee, D, et al. "2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines." Circulation, Vol 144, 28 Oct 2021. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001030.
