E2 ModeratePreliminaryPEM unclearCross-SectionalPeer-reviewedMachine draft
Index markers of chronic fatigue syndrome with dysfunction of TCA and urea cycles.
Yamano, Emi, Sugimoto, Masahiro, Hirayama, Akiyoshi et al. · Scientific reports · 2016 · DOI
Quick Summary
Researchers analyzed blood samples from ME/CFS patients and healthy people to look for chemical markers that could help diagnose the disease. They found that certain metabolites—molecules involved in energy production and waste removal—were abnormal in ME/CFS patients. Two specific chemical ratios in the blood showed promise as potential diagnostic tools, correctly identifying CFS patients about 75-80% of the time.
Why It Matters
ME/CFS currently lacks objective diagnostic tests, making diagnosis challenging and delaying treatment. This study provides evidence that specific blood metabolite abnormalities could form the basis for an objective diagnostic tool, potentially improving diagnostic accuracy and helping establish CFS as a biological disease rather than a psychiatric condition.
Observed Findings
- CFS patients showed significant differences in intermediate metabolite concentrations in TCA and urea cycles compared to healthy controls.
- The ornithine/citrulline ratio discriminated CFS from controls with AUC 0.801 in the training dataset (95% CI: 0.711-0.890, P<0.0001).
- The pyruvate/isocitrate ratio showed AUC 0.750 in the validation dataset (95% CI: 0.584-0.916, P=0.0069).
- A combination of two metabolite ratios achieved better discrimination than individual metabolites.
Inferred Conclusions
- Plasma metabolite ratios reflecting TCA and urea cycle dysfunction show promise as objective biomarkers for CFS diagnosis.
- A clinical diagnostic tool based on these metabolite ratios could potentially be developed to support CFS diagnosis.
- Metabolomic profiling may provide an objective, biochemical approach to diagnosing a disease previously lacking biological diagnostic markers.
Remaining Questions
- Do these metabolite abnormalities reflect central bioenergetic dysfunction in ME/CFS, and what underlying mechanisms cause the TCA and urea cycle dysfunction?
- Will these biomarkers perform well enough in larger, diverse clinical populations to be adopted in clinical practice?
- Do metabolite levels change with disease severity, treatment, or over time, and can they predict prognosis or treatment response?
What This Study Does Not Prove
This study does not prove that these metabolite abnormalities cause ME/CFS—only that they are associated with the disease. It does not establish whether these changes are primary features of CFS or secondary consequences of illness, activity limitation, or other factors. The modest validation performance (AUC 0.750) means this biomarker combination is not yet ready for clinical use without further refinement.
Tags
Symptom:Fatigue
Biomarker:MetabolomicsBlood Biomarker
Method Flag:Weak Case DefinitionSmall SampleExploratory Only
Metadata
- DOI
- 10.1038/srep34990
- PMID
- 27725700
- 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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