A STRATEGY FOR THE USE OF CARDIAC INJURY MARKERS (TROPONIN-I AND TROPONIN-T, CREATINE KINASE-MB MASS AND ISOFORMS, AND MYOGLOBIN) IN THE DIAGNOSIS OF ACUTE MYOCARDIAL-INFARCTION

Objective.-To design a strategy for cardiac injury marker testing in t he diagnosis of acute myocardial infarction. Design.-Prospective study . Group (n = 54 patients): evaluation of clinical performance. Specime ns collected at 0, 3, 6, and 12 (+/-1.5) hours after presentation. Wor ld Health Organization criteria were used for diagnosis of acute myoca rdial infarction. Group II (n = 57 patients): evaluation of temporal e volution. Time intervals 0 to 1.5, 1.5 to 4.5, 4.5 to 7.5, and 7.5 to 13.5 hours. Patients identified by positive creatine kinase-MB (CK-MB) mass or myoglobin. Fourteen patients in Group I qualified for Group I I. Hence, the total number of patients was 97. Setting.-A team of labo ratorians and clinicians at the University of California, Davis, hospi tal assessed the clinical performance and temporal evolution of serial CK-MB isoform, troponin I, and troponin T results in comparison to pa rallel CK-MB mass and myoglobin results. Main Outcome Measures.-Group I: sensitivity, specificity, and positive and negative predictive valu es. Group II: the time interval of the first positive result for each cardiac injury marker. Strategy and conclusions were based on study re sults and a literature review. Participants.-Emergency department pati ents with acute onset of chest pain and other complaints, possibly ind icative of myocardial ischemia, who were under evaluation for admissio n. Results.-Twenty-seven cases of acute myocardial infarction were doc umented. Group I: troponin I had the highest specificity (100%) and th e highest positive predictive value (100%); troponin I, troponin T, an d CK-MB mass had the highest sensitivity (90.0%); and the negative pre dictive values of troponin I, troponin T, and CK-MB mass were comparab le (97.8%, 97.6%, and 97.6%, respectively). Group II: early diagnosis (within 1.5 hours) was provided by both CK-MB isoforms and CK-MB mass, and then by myoglobin and troponins, in order of decreasing frequency , Conclusions.-Creatine kinase-MB mass, myoglobin, and troponin I were selected as the cardiac injury markers of choice at our institution. The strategy calls for serial testing of myoglobin and CK-MB mass init ially-and serially if warranted by heightened clinical suspicion-with troponin I added if indicated for (1) specific confirmation, (2) late presentation, or (3) risk stratification.