PLASMA OXIDASE ASSAY FOR SCREENING OF MYOCARDIAL-INFARCTION

The availability of techniques such as surgical reperfusion, angioplas ty, and thrombolysis for the treatment of acute myocardial infarction (AMI) has revived interest in seeking an early detectable biochemical marker diagnostic for AMI. Therefore, we investigated whether an unide ntified oxidase that is released by activated neutrophils at the onset of AMI could be used as an early diagnostic assay. The conversion by plasma oxidase of 1 mu M of adrenaline to 1 mu M of adrenochrome repre sents the plasma oxidase activity (POA) of 1 U/L. Fifty patients suspe cted of having AMI, 40% of whose electrocardiograms were nondiagnostic for AMI, were admitted to the coronary care unit, and venous blood sa mples were obtained for determination of the POA and creatine phosphok inase-MB levels. Healthy volunteers (n = 12) served as control subject s, and 8 patients with pneumonia whose leukocyte counts were greater t han 15,000 mu L were included in the study. In those with AMI (n = 22) , as determined by serial creatine phosphokinase-MB, the mean POA (+/- standard error of the mean) was 233 +/- 13 U/L, and in those with ang ina and no AMI (n = 28) was 127 +/- 5 U/L (P < 0.0001). In the control group, mean POA (+/- standard error of the mean) was 84 +/- 5 U/L (co ntrol versus angina; P < 0.01) and for those with infection was 214 +/ - 10 U/L. At admission, the creatine phosphokinase-MB was diagnostic f or only 12 of the 22 patients with AMI (sensitivity rate of 54%), wher eas in 21 of those patients, the POA values were diagnostic for AMI (s ensitivity rate of 95%). Determination of POA may represent an alterna tive sensitive method to screen for AMI or ischemia in patients with a nginal symptoms and no evidence of acute infection.