Have you already got that? Labels below search results by authoritative source (I guess so).
Check this search: http://www.google.com/search?complete=1&hl=en&rlz=1B3GGIC_enFR208FR227&q=migraine+more:tests_diagnosis&cx=disease_for_patients&sa=N&oi=coopctx&resnum=0&ct=col2&cd=1

The sources links redirects to Google Co-op, but I haven't suscribed to those links! Google health is coming wether you want it or not.

The subject is already discussed here (sorry): http://blogoscoped.com/forum/29834.html