Response to Letter Regarding Article, “Initial Lesion Volume Is an Independent Predictor of Clinical Stroke Outcome at Day 90: An Analysis of the Virtual International Stroke Trials Archive (VISTA) Database”

Abstract

Response: We thank the authors for their interest in our study and interesting suggestions that we have followed in some reanalyses. We believe, however, that the criticism regarding methodology of our article is largely unjustified. We have followed the suggestion to examine the interaction of the National Institutes of Health Stroke Scale (NIHSS) at baseline and lesion volume and indeed found an interaction ( P =0.02), but only on NIHSS at Day 90 as the end point, not for modified Rankin Scale (mRS; linear) or mortality. The interaction for the NIHSS end point suggests a mutual influence of both baseline parameters resulting in steepening of the baseline NIHSS regression at higher lesion volumes and vice versa. This comparably weak finding should however be regarded with caution at present. Considering the linear treatment of NIHSS, in biological systems, there is hardly any relationship of complex parameters that is really strictly linear; linear regression is a practical approximation that …