Using the Ratio of Phosphorylated to Non-phosphorylated Forms of Stress Kinase PKR as a Potential Diagnostic Test for ME/CFS.
Sweetman, Eiren, Tate, Warren P · Methods in molecular biology (Clifton, N.J.) · 2025 · DOI
Quick Summary
Researchers developed a new blood test that measures a specific immune protein called PKR in white blood cells to help diagnose ME/CFS. The test looks at whether PKR is in an active or inactive form—people with ME/CFS appear to have different patterns of active PKR compared to healthy people. If this method works well in larger studies, it could provide doctors with a simple, quick way to diagnose ME/CFS instead of waiting months while ruling out other illnesses.
Why It Matters
ME/CFS currently lacks an objective diagnostic biomarker, forcing patients through years of exclusionary testing and contributing to diagnostic delays and invalidation. A validated PKR phosphorylation ratio test could accelerate diagnosis, enable earlier intervention, support disease monitoring, and provide biological evidence that ME/CFS is a measurable organic illness.
Observed Findings
Phosphorylated PKR ratios differ between peripheral blood monocytes and neutrophils in ME/CFS patients compared to age and sex-matched controls
Protein kinase R was detected in cleaved, auto-phosphorylated, and active forms in samples from ME/CFS participants in previous studies
Specific antibodies can identify and quantify the phosphorylated-to-total PKR ratio using ELISA format
The method is feasible as a potential diagnostic approach for early acute stage ME/CFS
Inferred Conclusions
PKR phosphorylation status may serve as a measurable biomarker distinguishing ME/CFS from healthy controls
An ELISA-based PKR phosphorylation test could provide a simple, accessible diagnostic tool if validated in larger cohorts
This approach may enable both acute diagnosis and long-term disease status monitoring
Remaining Questions
What are the sensitivity and specificity of the PKR phosphorylation ratio test in large, diverse patient populations?
How does PKR phosphorylation status change over the disease course and in response to treatments?
Can the PKR ratio distinguish ME/CFS from other conditions that produce similar symptoms or fatigue?
What This Study Does Not Prove
This study does not prove that PKR phosphorylation is the cause of ME/CFS—only that the ratio differs between patients and controls. The small sample size and methods-development nature mean the test's sensitivity, specificity, and clinical utility remain unestablished and require independent validation. The findings do not indicate whether PKR activation is a primary driver of disease or a secondary consequence of the illness.