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Clinical Chemistry, Vol 19, 994-997, Copyright © 1973 by the American Association for Clinical Chemistry
1 Department of Pathology, Orange County Medical
Center, Orange, Calif. 92668; and The University of California, Irvine, Calif.
Direct assay of creatine kinase by the method of Siegel and Cohen with the Technicon "SMA 12/60" is compared with two indirect coupled-enzyme assay methods. The direct method was linear to greater than 2000 U/liter, whereas the indirect methods were linear to 250 and 1500 U/liter, with use of serial dilutions of a creatine kinase preparation. Increasing the activity of the auxiliary enzymes, hexokinase and glucose-6-phosphate dehydrogenase, in one of the coupled enzyme assay methods increased its linear range from 250 to 700 U/liter. The observed findings are explained on the basis of the fundamental differences between direct and indirect coupled-enzyme assay systems and, within the latter system, the effect of the activities of auxiliary enzymes.
Submitted on August 28, 1972
Accepted on June 4, 1973
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