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(Stroke. 2007;38:258.)
© 2007 American Heart Association, Inc.

Letters to the Editor

Response to Letter by Saver

Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, Calif

An extract of the first 250 words of the full text is provided, because this article has no abstract.

Response:

The principal purpose of our article¹ is didactic: we present a valid, straightforward method for comparing outcomes in 2 treatment groups if the basis of comparison is an ordinal response scale. The technique, based on the Mann-Whitney nonparametric statistic, is readily available to practitioners in most elementary statistics software programs. We illustrated the technique with data reproduced from the SAINT I trial of NXY-059 in acute ischemic stroke.²

In fact, the motivation for our article was the SAINT I publication.² A hallmark of rigorous science is reproducibility: can reported findings in the scientific literature be replicated independently? On reading the New England Journal of Medicine article, we were dismayed that the authors failed to provide sufficient information to allow us to verify their assertion of the "statistical significance" of one of the primary outcomes of the SAINT I trial, the shift in modified Rankin Scale (mRS) values in the NXY-059 intervention group relative to the control group. Indeed, even if we had been provided the raw data accruing from the SAINT I trial, we would have been unable to validate their declaration of statistical significance, as we would need to make educated guesses on how they undertook a stratified analysis. Though this may well be a reflection of our failings as data analysts, our frustration certainly would have been less palpable had the authors merely followed CONSORT guidelines³ for statistical reports of clinical trials.

A corollary development of the Mann-Whitney approach to the analysis of ordinal data is the . . . [Full Text of this Article]