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Bootstrap statistics of ECASS II data: just another post hoc analysis of a negative stroke trial?
R Stingele1, E Bluhmki, W Hacke
1Department of Neurology, University of Heidelberg, Germany. j62@ix.urz.uni-heidelberg.de
Unlabelled:
The results of the Second European-Australasian Acute Stroke Study (ECASS II) were negative with respect to the primary endpoint. This post hoc analysis of ECASS II data was designed to make the least number of a priori assumptions. 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 disadvantages of dichotomization. By reducing the number of a priori assumptions, the possibilities to modify the test result by adjusting the test procedure are minimized.
Results:
If rt-PA does not improve the outcome (null hypothesis), the probability of observing a difference of modified ranking scale equal or larger than the one observed in ECASS II is 0.047. We therefore rejected the null hypothesis.