SERIAL CREATININE KINASE (CK) MB TESTING DURING THE EMERGENCY DEPARTMENT EVALUATION OF CHEST PAIN - UTILITY OF A 2-HOUR DELTA-CK-MB OF +1.6NG ML/

Background Traditional methods of using creatinine kinase (CK)-MB io d iagnose acute myocardial necrosis rely on the total CK-MB exceeding a threshold of normalcy before being considered diagnostic. Because the CK-MB rapid immunoassay is both sensitive and precise, a small differe nce between two serial samples over an appropriate time interval may r esult in an increased sensitivity for acute myocardial infarction (AMI ) compared with traditional methods if an appropriate cutoff value is chosen. Methods and Results Baseline and 2-hour CK-MB immunoassay meas urements were performed in 710 patients with chest pain whose baseline CK-MB was less than two times upper limits of normal (<12 ng/ml) to d etermine whether a rise in CK-MB greater than or equal to+1.6 ng/ml is more sensitive and specific than an abnormal 2-hour CK-MB in the dete ction of patients with AMI during the initial emergency department eva luation of chest pain. The baseline (MBO) or 2-hour (MB2) CK-MB was co nsidered positive if the CK-M B level was greater than or equal to 6 n g/ml. MB Delta was defined as the difference of MB2 and MBO and was co nsidered positive if the value was greater than or equal to+1.6 ng/ml. A positive MB2 was more sensitive for the detection of AMI (75.2% vs 17.7%, p < 0.0001) than a positive MBO. A positive MB Delta was more s ensitive for the detection of AMI (93.8% vs 75.2%; p < 0.0001) than a positive MB2. There were no statistically significant differences in s pecificities for AMI for any test modality. Conclusions A rise in CK-M B of greater than or equal to+1.6 ng/ml in 2 hours is a useful marker of AMI during the initial emergency department evaluation of patients with chest pain.