To the Editor.—
The attempt by Peyser et al to objectively assess cognitive function with the Category Test in patients with multiple sclerosis (MS) (Archives 1980;37:437-440) suffers from the lack of an age-matched control group. Instead, the authors applied a "standard cut-off" score for the test, which is of questionable validity for their sample. This cut-off score was established on a sample of normal controls with an average age of 28 years,1 whereas their MS sample had an average age of 41 years. Error scores on the Category Test are directly related to age,2 a result that is not surprising in view of the complex abstractive capacities that the test demands. The control average for a group3 slightly less educated but comparable in age with the Peyser et al group had a mean error score of 59, a score slightly worse than the mean of 55 obtained
Binder LM. Control Groups for Multiple Sclerosis Tests. Arch Neurol. 1981;38(5):325. doi:10.1001/archneur.1981.00510050091023
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