July 1971


Am J Dis Child. 1971;122(1):85-86. doi:10.1001/archpedi.1971.02110010121025

To the Editor.—In a recent report, Katz and Liebman claimed that increased activity of creatine phosphokinase (CPK) was present in 32 of 85 children with a variety of acute or chronic disorders of the nervous system.1 In 29 of the 32 patients with increases, the values ranged between 1.4 and 7 international units (IU). (Activity should be reported as international units per liter or milliunits per milliliter.) Thirty two of 37 normal controls were reported to have no detectable CPK activity in cerebrospinal fluid (CSF) and in five others, the activity was reported to range between 0.48 and 1 IU. To measure the activity reported in the five normals with detectable CSF CPK levels, Katz and Liebman would have had to measure absorbance out to the fourth decimal place, surely beyond the capacity of any clinical spectrophotometer and taxing the limits of the most sophisticated research instrument. Extreme

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