Tilt table test

Proposed Diagnostic Criteria for ME/CFS by IOM
It would take a Tilt Table Test to diagnose Orthostatic Intolerance

Symptoms Predict the Outcome of Tilt Table Testing in CFS/ME/FM
"Chronic Fatigue Syndrome and Fibromyalgia are frequently associated with orthostatic intolerance, including Postural Orthostatic Tachycardia Syndrome, Symptomatic Orthostatic Tachycardia Syndrome, and Neurally Mediated Hypotension."