Immunochemical LD1Assay for Myocardial Infarction

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Abstract
The diagnostic efficiency of an immunochemical assay for LD1 (I-LD1) was compared with an electrophoretic procedure for this isoenzyme (E-LD1) in 100 consecutive patients hospitalized for a clinical suspicion of acute myocardial infarction (MI). All patients were investigated with a standard protocol including serial determinations of total creatine kinase (CK) and lactic dehydrogenase (LD) activities, CK and LD isoenzymes, and electrocardiograms. Thirty-two patients were diagnosed to have acute MI on the bases of positive CK-MB or EKG or both. The coefficients of variation for the intraassay and interassay precision of I-LD1 assay ranged from 3.12% to 7.69%. Direct correlation between the I-LD1 and E-LD1 was very satisfactory (r = .961; P = <.001). When the results of these two procedures were compared in terms of decision values for acute MI, there was agreement between them in 87 patients. At the cut-off point of 90 U/L, I-LD1 assay was 100% sensitive and 89% specific for acute MI; the corresponding figures for E-LD1 were 81% and 91%, respectively. The diagnostic efficiencies of the I-LD1 and E-LD1 procedures were 93% and 88%, respectively. A substantial saving in technologist time with the I-LD1 assay over the E-LD1 procedure was documented in this study.