Serial creatine kinase-MB results are a sensitive indicator of acute myocardial infarction in chest pain patients with nondiagnostic electrocardiograms: the second 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 infarction (MI) in patients presenting to the ED with chest pain and nondiagnostic ECGs.


METHODS
A prospective, observational test performance study was conducted. Hemodynamically stable patients aged > or = 25 years with chest discomfort, but without ECGs diagnostic for MI, were enrolled at 7 university teaching hospitals. Presenting ECGs showing > 1-mV ST-segment elevation in > or = 2 electrically contiguous leads were considered diagnostic for MI; patients with diagnostic ECGs on presentation were excluded. Real-time, serial CK-MB mass levels were obtained using a rapid serum immunochemical assay at the time of ED presentation (0-hour) and 3 hours later (3-hour). The following testing schemes were evaluated for their sensitivity and specificity for detection of MI during patient evaluation in the ED: 1) an elevated (> or = 8 ng/mL) presenting CK-MB level; 2) an elevated presenting and/or 3-hour CK-MB level; 3) a significant increase (i.e., > or = 3 ng/mL) within the range of normal limits for CK-MB concentrations during the 3-hour period (delta CK-MB); and/or 4) development of ST-segment elevation during 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 performance characteristics of serial CK-MBs for MI (and cumulative data for the additional ECG) were: [table: see text] The 0-hour to 3-hour CK-MB positive 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: [table: see text]


CONCLUSIONS
Serial CK-MB monoclonal antibody mass measurements in the ED can identify MI patients with initially nondiagnostic ECGs. CK-MB sensitivity significantly increases over 3 hours of observation of stable chest discomfort patients in the ED; it also increases as a function of the total interval from onset until enzyme measurement.
Young
G P
GP
Highland Hospital, Oakland, CA, Emergency Department, USA. garypyoung@aol.com
Gibler
W B
WB
Hedges
J R
JR
Hoekstra
J W
JW
Slovis
C
C
Aghababian
R
R
Smith
M
M
Rubison
M
M
Ellis
J
J
D000328:Adult; D000368:Aged; D000789:Angina, Unstable / Q000175:diagnosis* / Q000201:enzymology; D000911:Antibodies, Monoclonal; D015415:Biomarkers / Q000032:analysis; D016001:Confidence Intervals; D003402:Creatine Kinase / Q000032:analysis*; D003937:Diagnosis, Differential; D004562:Electrocardiography; D004635:Emergency Medicine; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000201:enzymology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012106:Research; D012680:Sensitivity and Specificity
D000911:Antibodies, Monoclonal; D015415:Biomarkers; D007527:Isoenzymes; D003402:Creatine Kinase