JSM 2004 - Toronto

Abstract #301853

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Activity Number: 119
Type: Contributed
Date/Time: Monday, August 9, 2004 : 10:30 AM to 12:20 PM
Sponsor: Biopharmaceutical Section
Abstract - #301853
Title: Efficacy without a Placebo Group in Mixed Factorial Designs
Author(s): Charles H. Goldsmith*+
Companies: McMaster University
Address: Centre for Evaluation of Medicines, Hamilton, ON, L8N 1G6, Canada
Keywords: placebo ; efficacy ; mixed factorial designs ; estimation ; esteoporosis ; bone loss
Abstract:

The new Helsinki guidelines for conducting experiments in humans suggest that if there is an effective therapy for a clinical condition, it is unethical to give a placebo to estimate the efficacy of a new therapy. Goldsmith showed that for two- or three-level factorial designs with two or more factors, efficacy can be demonstrated without a placebo group provided the model for the data does not contain any interactions with the new therapy. The two-level and three-level results are extended to designs with at least two mixed level factors, where no interactions with the new therapy permit the estimation of contrasts amongst the levels of the new therapy factor without having a placebo group. Estimable contrasts include efficacy of the new therapy. Suppose the new therapy has two levels: placebo and active, and the effective therapy has three levels: placebo, low dose, and high dose. From the five groups excluding the double placebo, two estimates of new therapy efficacy can be obtained from the nonplacebo levels of the known therapy and pooled to estimate new therapy efficacy. The results will be illustrated using a study with a 2x3 factorial design.

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