I am planning to conduct a sham-controlled study to compare the effect of non invasive brain stimulation modality at different cortical areas. I am going to use two different montages to compare between them and I need sham group to control the study.
My question is:
Can I enroll all the participants to the sham group (Placebo) before randomly assign them to one of the two experimental groups? (N.B. Adequate washout period will be given after sham stimulation) .. Is this scientifically sound methodology to fulfill the assumption of crossover, sham-controlled study design?
This way, you will not be studying the difference between each of the two active interventions and the placebo in a randomized fashion (semi-experimental design). Only the comparison of the active interventions is randomized. Did you consider a three-period randomized crossover design, where each person receives the placebo and the two interventions in a random fashion?
Thank you very much for your valuable suggestion Muhammad M Hammami James Leigh
I did not consider the three-period randomized crossover design because if stimulation A improves the patient during the first period, then stimulation B will have less opportunity to demonstrate its effectiveness when the patient cross over to stimulation B in the second period. Additionally, I could not find in the literature an adequate washout period after multiple real stimulation sessions.
So I think the best way is to randomize the assignment into three parallel groups.
Thank you again
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