Weighting of orthostatic intolerance time measurements with standing difficulty score stratifies ME/CFS symptom severity and analyte detection

Table 1 Symptoms and related physical signs based on the Canadian Criteria for ME/CFS diagnosis, presented by class, and as assessed at the CFS Discovery Clinic

Canadian criteria symptom classes	Role in CFS/ME diagnosis	Specific symptoms identified	Factor analysis (% variance)* ANOVA (p value)**
Post-exertional malaise and fatigue	Mandatory	Fatigue, malaise and/or pain post effort ≥ 24-h recovery	All symptoms are mandatory (100%)^#
Minimum 6-months fatigue	Mandatory	≥ 6-months unexplained fatigue	Symptom mandatory (100%)^#
Sleep disorder	Mandatory	Difficulty going to sleep Sleep during day	62% (p < 0.0001)
Pain	Mandatory	Pain (any region) Headache	87% (p < 0.0001) 71% (p = 0.118)
Neurological/cognitive manifestations	≥ 2 criteria required	Light, sound and/or smell sensitivity Confusion	62% (p < 0.0001) 38% (p < 0.0001)
		Autonomic
		Breathless	58% (p < 0.0001)
		Arrhythmia	42% (p < 0.0001)
Autonomic/neuroendocrine/immune manifestations	≥ 1 criteria for 2 of the 3 categories required	Gut
Autonomic/neuroendocrine/immune manifestations	≥ 1 criteria for 2 of the 3 categories required	Bloating, abdominal pain, diarrhoea	40% (p < 0.0001)
		Neuroendocrine
		Hot/Cold flushes	73% (p < 0.0001)
		Immune
		Tender glands, flulike symptoms, chemical (allergy) sensitivity	45% (p < 0.0001)

Identification of significant diagnostic criteria responses via factor analysis of a tetrachoric correlation matrix
Based on Canadian Criteria [1]
* Percentage variance explained, derived from factor analysis of tetrachoric correlation matrix across all CFS/ME severity classes, including healthy study controls
** p values calculated from ANOVA of factor scores across four classes of severity defined by weighted standing time (WST)
^#No (0%) healthy controls reported a minimum of 6-months fatigue, or post-exertional fatigue/malaise

ISSN: 1479-5876