USE OF A RAPID ASSAY OF SUBFORMS OF CREATINE-KINASE MB TO DIAGNOSE ORRULE OUT ACUTE MYOCARDIAL-INFARCTION

Background. Ruling out myocardial infarction in patients coming to the emergency room with chest pain is hindered by the lack of a specific early diagnostic marker. Less than 30 percent of patients admitted to coronary care units have infarction, resulting in substantial unnecess ary expenditures. We developed a rapid assay of the subforms of creati ne kinase MB (OK-MB) and prospectively analyzed its sensitivity and sp ecificity in diagnosing myocardial infarction in the first six hours a fter the onset of chest pain. Methods. In 1110 consecutive patients wh o came to the emergency room with chest pain, blood samples were colle cted every 30 to 60 minutes until at least 6 hours after the onset of symptoms; in patients who were then admitted to the hospital, samples were collected every 4 hours for up to 48 hours. The samples were anal yzed for CK-MB subforms, and the diagnosis of myocardial infarction wa s confirmed by conventional CK-MB analysis. Results. Of the 1110 patie nts evaluated, 121 had myocardial infarction. The sensitivity of the a ssay of OK-MB subforms to detect myocardial infarction in the first si x hours after the onset of symptoms was 95.7 percent, as compared with only 48 percent for the conventional CK-MB assay; the specificity was 93.9 percent among patients hospitalized without myocardial infarctio n and 96.2 percent among those sent home. Among the patients with myoc ardial infarction, definitive results of the subform assay were availa ble a mean (+/-SD) of 1.22+/-1.17 hours after their arrival in the eme rgency room. Conclusions. The assay of CK-MB subforms reliably detecte d myocardial infarction within the first six hours after the onset of symptoms, and its use could reduce admission to the coronary care unit by 50 to 70 percent, thereby reducing costs.