Fixed effects model with Group term [Two-Stage / GS Designs]

posted by VStus – Poland, 2016-10-20 13:54 (1505 d 02:36 ago) – Posting: # 16744
Views: 29,161

Dear mittyri,

Getting a little back to possible nightmare for BE studies assessed in Russia:

» It could be a nightmare for Russia, where the experts insist on the Group term in the model, but all other things should be like in EMA Guideline with all factors as fixed (does someone realize how many studies will be failed? The experts suggest not to pool the groups in this case like the FDA Guidance states!)

Why do you proceed to calculation of Point Estimate and Confidence Intervals using FDA Group Model 1 (those with Treatment*Group interaction) if it's not seems to be intended for anything more than assessment of statistical significance of this particular effect?

I've just gone through some historical studies (with groups) done at well-established CROs before EMA Q&A document regarding statistical model for TSDs became available. They assessed studies using FDA recommendations. Model 1 was used only to calculate significance of Treatment*Group interaction and nothing more! No MSE, PE and 90%CI print-outs for this model. After confirmation that effect is not significant, data was processed under FDA Group Model 2 with bioequivalence assessment.

Why not use the same strategy here? F and P seems to be equal between R and PNX, as well as between R and SAS PROC GLM.
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PS: FDA Group Model 1 produces weird results in regards to Point Estimate (if we get it directly from ANOVA table), potentially making a good trial useless. In one of examples PE traveled from 96% to 88% (sic!) for data where geometric means ratio was almost equal to LSMeans ratio.

Regards, VStus

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