Further observations on the incidence and nature of atypical creatine kinase activity.

The interference of atypical creatine kinase (CK; EC 2.7.3.2) with anion-exchange methods for the measurement of the CK-MB isoenzyme is now firmly established. False-positive results from this source are much more common than interferences caused by the BB isoenzyme. Atypical CK, at least in some patients, does not appear to be a genetic variant, nor could we relate it to a specific clinical diagnosis, to hypoxia, or to administration of a particular drug. Its behavior in an immuno-inhibition test for CK-B subunit indicates an immunological difference from the normal M subunit. Thus the change in immunological properties is associated with the altered electrophoretic properties. The variability of electrophoretic patterns suggests that atypical CK may represent multiple forms of creatine kinase rather than a unique entity.