- Last Update On : 2013-02-21
Recently, the American College of Cardiology (ACC) and the American Heart Association (AHA) issued new guidelines for the management of patients with unstable angina and non-ST segment elevation myocardial infarction (Circulation 2000; 102:1193-1209). At the same time, a joint committee of the European Society of Cardiology and ACC published a consensus document entitled the “Redefinition of MI” (JACC 2000; 36:959-69). These articles contained the following recommendations regarding cardiac marker laboratory testing.
- Troponin T or I is the preferred cardiac marker.
- CK-MB is an acceptable alternative, if troponin is not available.
- Total creatine kinase (CK) is no longer useful & should be discontinued.
- Troponin should be measured within 6 hours of the onset of symptoms.
- If the first troponin result is negative, a second sample should be obtained between 6 & 12 hours of symptom onset.
- Cardiac Marker results should be available within 30 to 60 minutes.
- An abnormal troponin result should be defined as >99th percentile of a normal population
- Troponin assay must have a low level of imprecision at the cutoff point (CV<10%).
Based on these recommendations, a group of physicians from Cardiology, Emergency Medicine and Pathology at our hospital decided to implement the following changes in cardiac marker testing.
- Create a new Cardiac Marker Panel for the Emergency Department that includes CK-MB & Troponin at 0, 3 & 6 hours after admission.
- Retain the current Acute Cardiac Injury Panel that includes CK-MB & Troponin at 0, 6 & 12 hours for admitted patients.
- Eliminate total CK from all cardiac panels.
Creation of the new Cardiac Marker Panel with shorter testing intervals facilitated more rapid decision-making in the Chest Pain Emergency Center. Retention of the 12-hour specimen for admitted patients prevented a missed diagnosis in patients who were late seroconvertors. Elimination of total CK had two major advantages. Patient charges decreased by $805,600 per year. Laboratory turnaround time was improved, because testing could be performed on one analyzer instead of two. Presently, none of the available troponin assays meets the stringent performance standard (CV<10% at a TnI value of 2.0) specified by ACC & AHA. Therefore, the laboratory continues to test for both CK-MB and TnI.