Bioequivalence and Bioavailability Forum

Hi d_labes and Helmut,

This really bugs me (from EMEA guidance)...

"In studies with more than two treatment arms (e.g. a three period study including two references, one from EU and another from USA, or a four period study including test and reference in fed and fasted states), the analysis for each comparison should be conducted excluding the data from the treatments that are not relevant for the comparison in question."

I have a dataset containing 4 treatments (from a 4-way 4-treatmens 4-sequence crossover study) and each treatment has different # of subjects (ie: A(T-Fast)=24, B(Ref Fast)=19, C(T-Fed)=22, D(Ref Fed)=24). I tried doing the stats as per the above statment (A vs D, C vs D, C vs A, D vs B) by removing the treatments that are not of interest but SAS gave me an error message for my SAS code

estimat1 = Estimate "A - D" Treatment 1 0 0 -1

"WARNING: More coefficients than levels specified for effect TREATMENT. Some coefficients will be ignored. NOTE: A vs D is not estimable." I got the same error message for each comparison.

Any reason why?

Thanks
John