Defining M.E. for diagnosis or research continues to be the subject of much debate.
Diagnostic criteria currently in use include:
A systematic review, Diagnosis and treatment of M.E./CFS, published by the Agency for Healthcare Research and Quality in the US in 2014, acknowledges that diagnostic studies of M.E. are limited by the lack of an accepted reference standard (case definition) or an agreed upon set of clinical criteria.
It concludes, “None of the current diagnostic methods have been adequately tested to identify patients with M.E. when diagnostic uncertainty exists […] More definitive studies are needed to fill the many research gaps in diagnosing and treating M.E.”