Detection of acute myocardial infarction by a new, sensitive and rabid method for determination of creatine kinase B-subunit activity

An immunoinhibition method for the assay of creatine kinase(CK) isoenzymes by continuous monitoring of the ATP formationin the CK reaction by a purified firefly luciferase reagenthas been developed. The sensitivity of the firefly assay ofATP makes it possible to assay CK-B subunit activity (CK-B)in serum down to 1 U/l. In healthy individuals CK-B varied between 2 and 12, mean 3U/l. A wide range of CK-B activity was observed after acutemyocardial infarction (AMI), intramuscular injection and surgerywith overlapping between these different categories. Thereforethe maximal change in CK-B activity (CK-B) was studied in 98patients admitted to a coronary care unit. In all 57 patientswithout a subsequent diagnosis of AMI according to conventionalcriteria CK-B was < 5 U/l. In all 41 patients with AMI CK-Bwas 5 U/l. In all healthy individuals CK-B was < 2 U/l.CK-B 5 U/l was found after i.m. injection and different kindsof surgery in three out of 60 patients. Thus, the present method for determination of CK activity hasbeen shown to possess high precision in low activities, to beas rapid as conventional methods and to be simple enough tobe used in a routine laboratory. With these properties the methodshould be suited for early diagnosis and early exclusion ofeven very small AMIs.