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August 26, 1974

Interpretation of CPK Activity

Author Affiliations

Pritzker School of Medicine Chicago

JAMA. 1974;229(9):1169. doi:10.1001/jama.1974.03230470021013

To the Editor.—  Although the article by Nevins et al (224:1382, 1973) "Pitfalls in Interpreting Serum Creatine Phosphokinase Activity" was generally excellent and comprehensive, the authors showed no awareness of what is likely to be in many urban hospitals in the United States the single most common "pitfall" in interpreting serum creatine phosphokinase (CPK) activity. I refer to the unequivocal demonstration that serum CPK activity is significantly greater in black males than white males and in black females than white females.1 We have replicated these findings in another study.2 The differences are fairly substantial. Nevins et al utilized the modified Oliver-Rosalki method and claimed the normal limits were 30 international units (IU) per liter for females, 50 IU/liter for males. These are the limits proposed by Calbiochem for their CPK assay kit, which employs this method, although Nevins et al did not indicate if they used this kit