Table 1.

Diagnostic criteria. Changes in criteria of CFS, GWI, and fibromyalgia over time are indicated from left to right. The 1990 fibromyalgia definition was the only one to require an objective finding (tenderness to pressure or systemic hyperalgesia). Postexertional malaise is proposed to be the most discriminating symptom in CFS and SEID criteria. * includes chronic idiopathic fatigue and atypical depression.

FM 1990	Oxford 1991	CFS “Fukuda” 1994	Chronic Multi-Symptom Illness (CMI) 1998	GWI “Kansas” 2000	Canadian Consensus Criteria ME/CFS 2003, 2007	FM 2010, 2011, 2016	SEID 2015
		Disability/ Reduced Quality of Life			Disability/Reduced Quality of Life		Disability/ Reduced Quality of Life
Tenderness
Widespread Pain		Myalgia Arthralgia	Musculoskeletal pain	Pain	Widespread Pain	Widespread Pain
	Fatigue	Fatigue	Fatigue	Fatigue	Fatigue	Fatigue	Fatigue
		Sleep		Sleep	Waking unrefreshed	Waking unrefreshed	Waking unrefreshed
		Post-exertional malaise		Post-exertional malaise	Post-exertional malaise		Post-exertional malaise
		Cognition	Cognition	Cognition	Cognition	Cognition	Cognition
			Mood	Mood
		Interoceptive symptoms
		Headache Sore throat Sore lymph nodes		Neurological Gastrointestinal Respiratory Skin	Neurological Autonomic Neuroendocrine Immune	Somatic symptoms	Orthostatic Intolerance
Key features for diagnosis
Pain + Tenderness	No exclusion *	Fatigue plus ≥4 of 8	≥1 chronic symptom in ≥2 categories	≥3 of 6 categories		Severity scores	Moderate or severe >50% of time