Boehringer immunoinhibition procedure for creatine kinase-MB evaluated and compared with column ion-exchange chromatography.

In determination of creatine kinase isoenzyme MB (CK-MB), the Boehringer immunoinhibition method gives a high and variable blank activity as compared with column-chromatography. Thus a correction must be applied. Furthermore, a second correction of 1% of total creatine kinase activity is necessary to compensate for nonspecific creatine phosphate-dependent activity. As a consequence, two immunoinhibition determinations--one for CK-MB and one for blank activity--and a determination of total creatine kinase are required. Use of the manufacturer's diagnostic criteria, on the basis of which suspected myocardial infarction is confirmed or eliminated, leads to a high frequency of false-negative conclusions.