The Autonomic Spectrum: POTS and Dysautonomia
The POTS defining criterion (heart rate increase ≥30 bpm on standing) has poor specificity — 10–15% of healthy controls meet it. Only 21% of ME/CFS patients with orthostatic symptoms meet formal POTS criteria, and symptom severity correlates poorly with heart rate magnitude (~2% of variance). POTS test results show poor day-to-day reproducibility. These limitations suggest that POTS may be a poorly specified diagnostic category rather than a coherent pathophysiological entity, and that the comorbidity with ME/CFS may partly reflect diagnostic threshold artefacts rather than shared biology.
Consequence: If POTS is a poorly validated construct, comparing ME/CFS to POTS is comparing one contested diagnosis to another — an unstable nosological comparison. The Shoenfeld “autoimmune autonomic spectrum” hypothesis (see Can Calprotectin Serve as an Objective PEM Biomarker?) proposes a resolution: ME/CFS, POTS, and related dysautonomias are all manifestations of autoimmune attack on the autonomic nervous system, with specific antibody targets (β2-adrenergic vs M3 muscarinic vs α1-adrenergic) determining whether presentation is predominantly orthostatic, cognitive, or mixed. This reframes the diagnostic categories as clinical phenotypes of a shared autoimmune process rather than distinct diseases.