Bootstrap statistics of ECASS II data: Just another post hoc analysis of anegative stroke trial?

The results of the Second European-Australasian Acute Stroke Study (ECASS I I) were negative with respect to the primary endpoint. This post hoc analys is of ECASS II data was designed to make the least number of a priori assum ptions. This is accomplished by a bootstrap-based hypothesis test on a non- parametric test statistic. No assumptions are made on shape or variance of population distributions and the method does not suffer from the disadvanta ges of dichotomization. By reducing the number of a priori assumptions, the possibilities to modify the test result by adjusting the test procedure ar e minimized. Results: If rt-PA does not improve the outcome (null hypothesi s), the probability of observing a difference of modified ranking scale equ al or larger than the one observed in ECASS II is 0.047. We therefore rejec ted the null hypothesis. Copyright (C) 2001 S. Karger AG, Basel.