A simple analysis of crossover studies with one-group interaction.
The crossover trial has an intuitive appeal to clinicians because each patient is use as his own control. Thus, between-subject variability of symptoms is eliminated. However, this study design suffers frequently from the bias of treatment-by-period interaction. If, for example, the effect of the first treatment period carries on into the next one, then it influences the response to the later period (carryover effect). A second problem is that the standard approach (Hills-Armitage analysis) for interaction has little power. This led the FDA and some statisticians to discourage the use of crossovers. In the present report I take issue with the common clinical situation where there is carryover effect in only one of the groups of a trial and present a simplified analysis for this situation with more power than the standard analysis.
Cleophas
T J
TJ
Department of Medicine, Merwede Hospital, Sliedrecht-Dordrecht, Netherlands.
D000704:Analysis of Variance; D018849:Controlled Clinical Trials as Topic; D018592:Cross-Over Studies; D015233:Models, Statistical; D014481:United States; D014486:United States Food and Drug Administration