Diagnostic efficacy of a new enzyme immunoassay for creatine kinase MB isoenzyme

A new commercial enzyme immunoassay kit for quantification of creatine kinase-MB (CK-MB) isoenzyme was compared with its electrophoretic determination with respect to efficacy in diagnosis of acute myocardial infarction. Enzygnost CK-MB (Behring Diagnostics) is a solid-phase "sandwich"-type enzyme immunoassay with antibodies to the B-subunit coated on plastic tubes and peroxidase-conjugated antibodies to the M-subunit added after incubation with sample. This kit is designed to measure only CK-MB and not CK-MM, CK-BB, adenylate kinase, or atypical CK molecules. The linear-regression equation comparing the two methods was: Enzygnost = 0.98 . electrophoresis - 0.72, with a correlation coefficient of r = 0.967 (n = 143). For 51 patients admitted for diagnosis of possible acute myocardial infarction, the Enzygnost kit achieved 100% sensitivity, specificity, and efficiency in predicting the correct diagnosis. Corresponding values for the electrophoretic assay were: 95.5% sensitivity, 93.1% specificity, and 94.1% efficiency. We conclude that this kit method provides an excellent alternative to electrophoresis.