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CLINICAL RESEARCH: ACUTE CORONARY SYNDROME

Frequency and Clinical Implications of Discordant Creatine Kinase-MB and Troponin Measurements in Acute Coronary Syndromes

L. Kristin Newby, MD, MHS, FACC^_*,_*, Matthew T. Roe, MD, MHS, FACC^_*, Anita Y. Chen, MS^_*, E. Magnus Ohman, MD, FACC, Robert H. Christenson, PhD, Charles V. Pollack, Jr, MD, MA, James W. Hoekstra, MD^||, W. Frank Peacock, MD^¶, Robert A. Harrington, MD, FACC^_*, Robert L. Jesse, MD, PhD, FACC^_**, W. Brian Gibler, MD, Eric D. Peterson, MD, MPH, FACC^_* for the CRUSADE Investigators

^_* Division of Cardiology and Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina
Division of Cardiology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina
Department of Pathology, University of Maryland, Baltimore, Maryland
Department of Emergency Medicine, Pennsylvania Hospital, Philadelphia, Pennsylvania
^|| Department of Emergency Medicine, Wake Forest University Health Sciences, Winston-Salem, North Carolina
^¶ Department of Emergency Medicine, Cleveland Clinic Foundation, Cleveland, Ohio
^_** Division of Cardiology, Medical College of Virginia and Veterans Administration Medical Center, Richmond, Virginia
Department of Emergency Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio

Manuscript received May 18, 2005; revised manuscript received July 24, 2005, accepted August 1, 2005.

^_* Reprint requests and correspondence: Dr. L. Kristin Newby, Duke Clinical Research Institute, P.O. Box 17969, Durham, North Carolina 27715-7969. (Email: newby001{at}mc.duke.edu).

OBJECTIVES: We sought to evaluate the association between discordant cardiac marker results and in-hospital mortality and treatment patterns in patients with non–ST-segment elevation acute coronary syndromes (NSTE ACS).

BACKGROUND: Creatine kinase-MB (CK-MB) and cardiac troponins (cTn) are often measured concurrently in patients with NSTE ACS. The significance of discordant CK-MB and cTn results is unknown.

METHODS: Among 29,357 ACS patients in the CRUSADE initiative who had both CK-MB and cTn measured during the first 36 hours, we examined relationships of four marker combinations (CK-MB–/cTn–, CK-MB+/cTn–, CK-MB–/cTn+, and CK-MB+/cTn+) with mortality and American College of Cardiology/American Heart Association guidelines-recommended acute care.

RESULTS: The CK-MB and cTn results were discordant in 28% of patients (CK-MB+/cTn–, 10%; CK-MB–/cTn+, 18%). In-hospital mortality was 2.7% among CK-MB–/cTn– patients; 3.0%, CK-MB+/cTn–; 4.5%, CK-MB–/cTn+; and 5.9%, CK-MB+/cTn+. After adjustment for other presenting risk factors, patients with CK-MB+/cTn– had a mortality odds ratio (OR) of 1.02 (95% confidence interval [CI] 0.75 to 1.38), those with CK-MB–/cTn+ had an OR of 1.15 (95% CI 0.86 to 1.54), and those with CK-MB+/cTn+ had an OR of 1.53 (95% CI 1.18 to 1.98). Despite variable risk, patients with CK-MB+/cTn– and CK-MB–/cTn+ were treated similarly with early antithrombotic agents and catheter-based interventions.

CONCLUSIONS: Among patients with NSTE ACS, an elevated troponin level identifies patients at increased acute risk regardless of CK-MB status, but an isolated CK-MB+ status has limited prognostic value. Recognition of these risk differences may contribute to more appropriate early use of antithrombotic therapy and invasive management for all cTn+ patients.

Abbreviations and Acronyms   ACC = American College of Cardiology/   ACS = acute coronary syndrome   AHA = American Heart Association   CI = confidence interval   CK-MB = creatine kinase-MB   CRUSADE = Can Rapid Risk stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the ACC/AHA Guidelines   cTn = cardiac troponin   NSTE = non–ST-segment elevation   OR = odds ratio   ULN = upper limit of normal

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