SERIAL CREATINE KINASE-MB RESULTS ARE A SENSITIVE INDICATOR OF ACUTE MYOCARDIAL-INFARCTION IN CHEST PAIN PATIENTS WITH NONDIAGNOSTIC ELECTROCARDIOGRAMS - THE 2ND EMERGENCY-MEDICINE CARDIAC RESEARCH GROUP-STUDY

Objective: To determine the test performance characteristics of serial creatine kinase-MB (CK-MB) mass measurements for acute myocardial inf arction (MI) in patients presenting to the ED with chest pain and nond iagnostic ECGs. Methods: A prospective, observational test performance study was conducted. Hemodynamically stable patients aged greater tha n or equal to 25 years with chest discomfort, but without ECGs diagnos tic for MI, were enrolled at 7 university teaching hospitals. Presenti ng ECGs showing >1-mV ST-segment elevation in greater than or equal to 2 electrically contiguous leads were considered diagnostic for MI; pa tients with diagnostic ECGs on presentation were excluded. Real-time, serial CK-MB mass levels were obtained using a rapid serum immunochemi cal assay at the time of ED presentation (0-hour) and 3 hours later (3 -hour). The following testing schemes were evaluated for their sensiti vity and specificity for detection of MI during patient evaluation in the ED: 1) an elevated (greater than or equal to 8 ng/mL) presenting C K-MB level; 2) an elevated presenting and/or 3-hour CK-MB level; 3) a significant increase (i.e., greater than or equal to 3 ng/mL) within t he range of normal limits for CK-MB concentrations during the 3-hour p eriod (Delta CK-MB); and/or 4) development of ST-segment elevation dur ing the 3 hours (second ECG). Results: Of the 1,042 patients enrolled, 777 (74.6%) were hospitalized, including all 67 MI patients (8.6% of admissions). As a function of duration of time in the ED, the test per formance characteristics of serial CK-MBs for MI (and cumulative data for the additional ECG) were: [GRAPHICS] The 0-hour to 3-hour CK-MB po sitive and negative predictive values were 52% to 55% and 96% to 99%, respectively. The sensitivities of serial CK-MB results as a function of the interval following chest discomfort onset were: [GRAPHICS] Conc lusion: Serial CK-MB monoclonal antibody mass measurements in the ED c an identify MI patients with initially nondiagnostic ECGs. CK-MB sensi tivity significantly increases over 3 hours of observation of stable c hest discomfort patients in the ED; it also increases as a function of the total interval from onset until enzyme measurement.