Dear Experts,
I used TBSS to compare the differences between 3 groups of patients with Parkinson's disease at baseline and change at follow-up. In my data analyses, when performing the FSL randomisation I used age, sex, education, and levo-dopa equivalent dose and when appropriate, interval between scans as covariates. I have submitted the paper for publication and one of the reviewers criticised that approach by saying that FSL randomisation can only take 2 covariates (see next):
"The three study groups were different in terms of age, education, interval between scans. Thus, these variables have been added as nuisance covariates, along with gender and levodopa equivalent daily dose. This may severely limit the consistency of findings, as the permutation test performed with randomise FSL tool can be weaken by using more than two covariates."
Is that true? Do we have evidence for that? What is the best approach for me to respond to that?
Regards,
Thais Minett
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