In chapter 9.7 you may find a proposal for an algorithm for treatment of children with ADHD, including the Restricted Elimination Diet (RED).  Children who respond well to the diet may be diagnosed with Food-induced (FI-ADHD). In these children, a hypersensitivity to certain foods is a causal factor of ADHD.

Children who do not show behavioral improvements following the RED may be diagnosed with classic ADHD (C-ADHD). The implementation is described in chapter 9.7. (page 203-210).

A schematic overview of the ADHD diagnostic prodecure, including the RED can be found here. (page 205)