THE POTENTIAL UTILITY OF A RAPID CK-MB ASSAY IN EVALUATING EMERGENCY DEPARTMENT PATIENTS WITH POSSIBLE MYOCARDIAL-INFARCTION

Study objectives: To determine the sensitivity, specificity, and predictive values of a new rapid creatine kinase-MB (R-CK-MB) assay compared with a standard CK-MB (S-CK-MB) assay and to determine its potential use in the evaluation of emergency department patients with possible myocardial infarction. Design: Retrospective patient identification with subsequent testing of excess sera for CK-MB and total CK using an identity-unlinked procedure. Setting: Large, urban, teaching hospital ED. Participants: All adult patients with excess sera and one of several defined presentations chosen to identify those with possible myocardial ischemia or infarction. Patients with clearly documented noncardiac etiologies of their symptoms or signs were excluded. Main results: The sensitivity, specificity, and positive and negative predictive values of 271 patient specimens for the R-CK-MB assay compared with the S-CK-MB assay were 100%, 96.8%, 75.0%, and 100%, respectively. The R-CK-MB assay was positive for 32 patients (11.8%). Of these, eight (25.0%) were admitted to unmonitored beds, and five (15.6%) were discharged home. All of these 13 patients had initial ECGs without evidence of ischemia or infarction. On follow-up, at least eight of the 13 had evidence of infarction. Conclusion: The R-CK-MB assay demonstrated high sensitivity and specificity compared with the S-CK-MB assay. When used for patients in whom a cardiac care unit admission is not considered, the rapid assay may identify some patients with unsuspected myocardial infarction and prevent inadvertent discharge or admission to unmonitored beds.