ImmunoinhibitionandAutomatedColumnChromatographyComparedfor Assayof CreatineKinaselsoenzymeMB in Serum

We examined sera from sixdifferent groupsofpatientsfor CK-MB activity by means of two commercially available tests,an immunoinhibitionmethod (E. Merck) and the CK-MB test as used with the aca (Du Pont). In the first group of patients (suspicion of myocardial infarction) the correlationbetween the two methods was good: r = 0.9191, y = 1.068x0.888, = 18.7 U/L, = 19.0 U/L. Inthe second group,patientswithhighadenylatekinase activity, no interference was detectable on the aca, whereas the immunoinhibitionmethod yielded falsely high CK-MB values.The thirdgroup consistedofpersons with macro-CK-BB in their serum. Inthe immunoinhibitiontest these patients usually showed a high CK-MB:total CK ratio, whereas such results were rarely found for the aca. The fourthgroup, patientswith a differentelectrophoretic mobilityof theirCK-isoenzymes (migrationof an active band towards the cathode), were detected by the immunoinhibition method (high ratio of CK-MB to total CK), but not with the aca. Inthepresence of free CK-BB (group five) the immunoinhibition testresultedin“falsely” high CK-MB values, whereas CK-BB was retained on the columnof the aca. Inskeletalmuscle diseases(groupsix)resultsby the two methods differed, values for CK-MB on the aca being much higher.Itwas demonstrated experimentally that this was due to CK-MM with altered surface charge.