LD1 and several ratios of lactate dehydrogenase isoenzymes in acute myocardial infarction.

The sensitivity and specificity of three parameters--ECG, creatine kinase MB isoenzyme and LD isoenzymes--were compared in 385 consecutive patients hospitalized for clinically suspected acute myocardial infarction (MI). In 147 patients acute MI was diagnosed on the basis of three parameters. In the remaining 238 patients acute MI was ruled out. Decision values for LD1, LD1/total LD, LD1/(LD2 + LD3 + LD4 + LD5), and the sum of LD1/LD2 + LD1/total LD + LD1/LD2 + LD3 + LD4 + LD5) were selected as 70 U/L, 0.33, 0.5, and 1.79, respectively for the test positivity of LD isoenzymes for acute MI. These new criteria, with the decision values, are proposed as test positivity of CK-MB and LD isoenzymes for acute myocardial infarction.