IS DETERMINATION OF CREATINE KINASE-2 AFTER ELECTROPHORETIC SEPARATION ACCURATE

Since 1991, the Ontario Laboratory Proficiency Testing Program has ass essed the analytical performance of creatine kinase (CK; EC 2.7.3.2) i spenzyme-2, using fresh human serum supplemented with purified human C K isoenzymes. In Ontario, the 142 laboratories licensed to analyze CK- 2 use a variety of methods: electrophoresis-based, immunoinhibition, a nd mass assays. During a 1992 survey, duplicate CK-2 samples with diff erent total CK activities showed poorer precision when analyzed after electrophoretic separation than by any other method. A 1993 survey des igned to validate these observations conclusively showed that electrop horesis-based assays are subject to a bias proportional to the total C K activity. These survey results were confirmed by studies with select ed patients' specimens. We therefore conclude that electrophoresis-bas ed assays may not warrant their reputation as the gold standard for CK isoenzyme measurement.