Neuroepidemiology. Part II: Assessment of therapeutic trials

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Abstract
The gold standard for therapeutic trials is the randomized, double‐blind, placebo‐controlled study design. Lack of blindness and placebo makes tenuous the attribution of results to the specific agent; lack of randomization between concurrent and comparable groups makes it impossible. The chi‐square test of the null hypothesis of no difference between treatment groups is the best method of assessment, as no overall rating system used in neurology is a true numerical scale but at best a rank‐order scale. If quantitation of results is desired, a nonparametric rank‐order test is necessary. Results over time can be assessed with a logrank (life‐table) test for single events as end point, and by chi‐square or rank‐order tests for multiple events among individual patients.