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My point is all Dx criteria for ME are basically quite arbitrary.
Not even the Fukuda criteria were entirely arbitrary. They were chosen based upon a theoretical model (and studied to a significant degree by Dr. Jason who has shown that they performed according to the psychosocial model). The question at hand is our understanding of the performance characteristics for a particular set of criteria. We can chose to study and understand or we can throw up our hands and say they don't matter or they can never be fully understood. On this we may simply have to disagree as to the wisest route.