Natural killer cytotoxicity in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): a multi-site clinical assessment of ME/CFS (MCAM) sub-study.
Querec, Troy D, Lin, Jin-Mann S, Chen, Yang et al. · Journal of translational medicine · 2023 · DOI
Quick Summary
Researchers tested whether a specific immune cell function called natural killer (NK) cytotoxicity could be a reliable blood test to help diagnose ME/CFS. They compared 174 people with ME/CFS to 86 healthy people and found no meaningful difference between the two groups. This means the test is not accurate enough to use in clinics right now, and scientists need to keep searching for better biological markers of ME/CFS.
Why It Matters
This rigorous multi-site study addresses a significant gap by systematically evaluating NK cytotoxicity as a potential diagnostic biomarker for ME/CFS using standardized methodology. A validated, clinically available blood test would help patients obtain faster, more reliable diagnoses and improve research standardization. This negative finding redirects scientific effort toward identifying more promising immune abnormalities.
Observed Findings
NK cytotoxicity showed large individual variation in both ME/CFS (34.1%, IQR 22.4-44.3%) and healthy control groups (33.6%, IQR 22.9-43.7%) with no statistically significant difference (p=0.79).
No associations were found between NK cytotoxicity and standardized questionnaire scores measuring ME/CFS illness domains.
NK cytotoxicity showed no correlation with self-reported physical and mental well-being or health factors including infection history, obesity, smoking status, and comorbid conditions.
Inferred Conclusions
NK cell cytotoxicity measured by this overnight-shipping-validated assay is not suitable for clinical implementation as a ME/CFS diagnostic tool.
The substantial overlap in cytotoxicity values between patients and controls suggests this single immune parameter does not reliably distinguish ME/CFS populations.
Future research should investigate alternative immune pathways and biomarkers more likely to contribute to ME/CFS pathophysiology.
Remaining Questions
What other immune parameters (NK cell subsets, cytokine profiles, T cell function, complement activation) might better distinguish ME/CFS patients from controls?
Does NK cytotoxicity dysfunction occur in specific ME/CFS patient subgroups not detected in aggregate population-level analyses?
Why do some earlier studies report reduced NK cytotoxicity in ME/CFS while this larger multi-site study found no difference, and how can these discrepancies be resolved?
What This Study Does Not Prove
This study does not prove that immune dysfunction is absent in ME/CFS—only that NK cytotoxicity measured by this specific assay is not a useful diagnostic marker. The findings do not eliminate the possibility that other immune parameters (cytokine profiles, T cell function, B cell abnormalities) may still be relevant to ME/CFS pathophysiology. Lack of difference between groups does not rule out NK dysfunction as a contributing factor in subsets of patients.