Immunoenzymometric assay of creatine kinase with monoclonal antibodies to the MB isoenzyme compared with electrophoresis.

We compare a "second-generation" immunoenzymometric assay (Tandem-E CKMB II) for creatine kinase (EC 2.7.3.2) MB with its electrophoretic (Beckman Paragon system) determination. In the former, two monoclonal antibodies are directed against the B and M subunits. We evaluated 502 samples from 253 patients. Precision, linearity, and analytical recovery for both assays were excellent. The two methods correlated well (r = 0.936). The reference interval for individuals with no suspected cardiac disorder was 0-6.0 micrograms/L; that for non-infarct patients was 0-18.0 micrograms/L. Peak CK-MB values determined by the two assays agreed for 95% of the patients, in terms of exceeding the normal reference interval or not. Diagnostic efficiencies were 86% (Tandem) and 88% (electrophoresis). The immunoenzymometric assay showed no cross reaction with other CK isoenzymes. Both assay methods performed well in detecting CK-MB, although there were some false positives by both methods, as judged from electrocardiographic results. When total CK for the Tandem assay exceeds 2000 U/L, we recommend calculation of a ratio (CK-MB, micrograms/L:total CK, U/L).