E2 ModeratePreliminaryPEM unclearCross-SectionalPeer-reviewedMachine draft
Blood rheology and myalgic encephalomyelitis: a pilot study.
Simpson, L O, Shand, B I, Olds, R J · Pathology · 1986 · DOI
Quick Summary
This study examined whether blood flows differently in people with ME/CFS compared to healthy people. Researchers tested blood samples and found that in the early stages of ME/CFS, blood may not flow as easily through tiny blood vessels, which could reduce oxygen delivery to tissues. However, in long-term ME/CFS, these blood flow problems were not observed.
Why It Matters
Blood flow problems are a plausible mechanism for ME/CFS symptoms, particularly post-exertional malaise and microvascular dysfunction. This study provides early evidence that rheological changes may distinguish acute from chronic ME/CFS phases, potentially guiding future diagnostic or treatment approaches targeting circulation.
Observed Findings
- Female subjects with ME/CFS showed significantly different blood filterability at lowest pressure (2.5 cm H₂O) compared to controls.
- Average blood viscosity was numerically different between ME/CFS and control groups but did not reach statistical significance.
- Rheological abnormalities appeared associated with acute ME/CFS phase but not chronic phase.
Inferred Conclusions
- Acute ME/CFS may involve blood rheological changes that could impair microcirculatory blood flow.
- Chronic ME/CFS does not appear to be associated with persistent rheological abnormalities.
- Blood filterability may be a more sensitive marker of disease phase than viscosity alone.
Remaining Questions
- Do rheological changes correlate with specific ME/CFS symptoms or functional impairment?
- What proportion of ME/CFS patients show these rheological abnormalities, and are there responders and non-responders?
- Do rheological properties normalize as acute disease transitions to chronic phase, or do they reflect different disease trajectories?
- How do these blood flow changes relate to post-exertional malaise or exercise intolerance?
What This Study Does Not Prove
This pilot study does not prove that blood rheology abnormalities cause ME/CFS symptoms or that they are present in all patients. The cross-sectional design cannot establish whether rheological changes precede symptom onset, and the small sample size means findings may not generalize to the broader ME/CFS population. Additionally, correlation between filtration changes and clinical outcomes was not established.
Tags
Symptom:Fatigue
Biomarker:Blood Biomarker
Method Flag:Weak Case DefinitionSmall SampleExploratory Only
Metadata
- DOI
- 10.3109/00313028609059457
- PMID
- 3093959
- Review status
- Machine draft
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 10 April 2026
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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