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June 19, 1981

MB Fraction of Creatine Kinase

Author Affiliations

The Malden Hospital Malden, Mass

JAMA. 1981;245(23):2393-2394. doi:10.1001/jama.1981.03310480013009

To the Editor.—  The possibly unique case of alcohol-related, chronic myopathy presented by Siegel and Dawson (1980;244:580) is a timely reminder that the MB isoenzyme of creatine kinase (CK-MB) may be detected in the presence of extreme elevations of skeletal muscle CK, especially when the skeletal muscle disorder is of a chronic nature. They mention that serial dilutions of sera with markedly elevated CK with CK-MB fractions result in disappearance of the MB band in those cases with skeletal muscle disease and persistence of the MB band in cases of bone fide myocardial infarction (MI).There is no doubt that the dilution technique permits a more appropriate enzyme-substrate ratio and improves determination of relative amounts of isoenzyme fractions in sera with marked elevations of CK; unfortunately, the procedure may also obscure MB fractions originating in the heart. Their patient exhibited CK elevations to 17,800 IU/L, while their MI control subject's