Serum LD-1 activity in suspected acute myocardial infarction

We have studied the diagnostic value of measuring lactate dehydrogenase (LD) isoenzyme 1 in serum of 331 cases of suspected acute myocardial infarction (AMI). At a discriminatory level of 200 U/L (Scandinavian Committee on Enzymes, recommended method for the determination of LD) LD 1 verified the diagnosis in 96% of the AMI cases and excluded it in 96% of the not-AMI cases when samples were drawn 24-72 h after onset of pain. The correlation between 24-h S-LD-1 and 16-h S-CK B activities was 0.94 in the AMI cases. We found that quantitation of serum LD-1 is diagnostically more reliable than the serum LD-1/LD ratio.