E2 ModerateModerate confidencePEM unclearCross-SectionalPeer-reviewedReviewed
Evaluating Routine Blood Tests According to Clinical Symptoms and Diagnostic Criteria in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
Baklund, Ingrid H, Dammen, Toril, Moum, Torbjørn Åge et al. · Journal of clinical medicine · 2021 · DOI
Quick Summary
Researchers compared blood test results from 149 ME/CFS patients with 264 healthy people to look for differences. They found that ME/CFS patients had higher levels of inflammation markers and certain blood cells, along with lower potassium and muscle enzyme levels. These differences suggest that ME/CFS may involve both inflammation and possible muscle or metabolic problems.
Why It Matters
This study provides objective laboratory evidence that ME/CFS patients show distinct blood abnormalities compared to healthy individuals, potentially supporting biological validation of the condition. Identifying these patterns may eventually help clinicians recognize ME/CFS through routine blood work and guide future research into disease mechanisms.
Observed Findings
- ME/CFS patients had elevated inflammatory markers: sedimentation rate, leukocytes, lymphocytes, neutrophils, and monocytes compared to controls.
- ME/CFS patients had higher vitamin B12 levels (mean difference: 83.43 pg/mL) and lower potassium levels than controls.
- ME/CFS patients showed lower creatine kinase (CK) and creatinine levels, suggesting possible muscle and metabolic abnormalities.
- ME/CFS patients had higher low-density lipoprotein (LDL) cholesterol compared to healthy controls.
Inferred Conclusions
- Multiple blood test abnormalities in ME/CFS patients point toward underlying systemic inflammation and immune activation.
- Reduced CK and creatinine levels suggest muscle damage and metabolic dysfunction as potential disease mechanisms.
- Routine blood work may reveal objective biological markers distinguishing ME/CFS patients from healthy individuals.
Remaining Questions
- Do these blood abnormalities persist over time, or do they fluctuate with disease severity and symptom changes?
- Are these findings specific to ME/CFS, or do they overlap with other chronic conditions, limiting diagnostic specificity?
- What is the mechanistic relationship between these blood test changes and core ME/CFS symptoms like post-exertional malaise?
What This Study Does Not Prove
This study does not prove that these blood test changes cause ME/CFS symptoms or that they are specific to ME/CFS alone. The cross-sectional design cannot establish whether these abnormalities are present before symptom onset or develop as a consequence of illness. Additionally, while differences exist statistically, their clinical significance and diagnostic utility in individual patients remain unclear.
Tags
Symptom:Fatigue
Biomarker:Blood Biomarker
Method Flag:PEM Not DefinedExploratory Only
Metadata
- DOI
- 10.3390/jcm10143105
- PMID
- 34300271
- Review status
- Editor reviewed
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 12 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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