Hello, Dr. Viechtbauer.
 
I am trying to perform a meta-analyis on a group of before-after studies using Metafor. I read your webpage including your correspondence with Dr. Dewey (https://stat.ethz.ch/pipermail/r-help/2012-April/308946.html), who also conducted a similar study. These information is very hepful, but I have one additonal question which I wonder if you can give me some instruction. The question is as follow:
 
These studies which we are trying to analyze are performed on the same subject before and after the adminstration of intervention. Most studies reported the the Mean±SD of percentage change, i.e., the Mean±SD of (value of ‘after’-value of ‘before’)/value of ‘before’×100%，without reporting the Mean±SD of value of ‘after’ or value of ‘before’. So I want to know if it is possible to perform meta-analyis using the value of percentage change, and if it is possible to calculate the ‘sdi’ (the standard deviation of the change scores) using the SD of percentage change.
 
Thank you very much, I am looking forward to your reply.
 
With best wishes.
 



Qiang Yue M.D.
Visiting Scholar of IMHR, University of Ottawa
1145 Carling Avenue, K1Z 7K4, Ottawa, ON, Canada
Tel: 613-722-6521 ext. 6554
Associate Professor of Radiology
Department of Radiology, West China Hospital, Sichuan University
Chengdu, 610041, China
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