Blood parameters differentiate post COVID-19 condition from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia.
Giménez-Orenga, Karen, Pierquin, Justine, Brunel, Joanna et al. · Brain, behavior, & immunity - health · 2025 · DOI
Quick Summary
Researchers measured specific proteins and immune markers in the blood of people with post-COVID-19 condition, ME/CFS, and fibromyalgia to see if they could tell these conditions apart. They found that certain blood markers could distinguish post-COVID-19 condition from the other two conditions with very high accuracy, suggesting these illnesses may involve different immune patterns even though their symptoms overlap significantly.
Why It Matters
Accurate differential diagnosis between post-COVID-19 condition, ME/CFS, and fibromyalgia remains clinically challenging due to overlapping symptoms; this study provides potential objective blood-based biomarkers that could improve diagnostic accuracy and guide targeted treatments. Identifying distinct immunological signatures may open therapeutic pathways specific to each condition and help explain why some COVID-19 patients develop ME/CFS-like illness while others do not.
Observed Findings
HERV-W ENV protein was detected in blood samples from post-COVID-19 condition, ME/CFS, and fibromyalgia patients, as well as in prepandemic ME/CFS and fibromyalgia cases.
Certain biomarker combinations (including antibody isotypes, cytokines, and NfL levels) showed 100% sensitivity and up to 71.9% specificity for discriminating post-COVID-19 condition from other groups.
Measured biomarkers demonstrated moderate-to-strong correlations with patient-reported symptoms of fatigue, pain, cognitive dysfunction, and sleep disturbance.
Immunological response patterns (IgM, IgG, IgA, IgE against SARS-CoV-2 antigens) differed between post-COVID-19 condition and the other two conditions.
Inferred Conclusions
Distinct blood biomarker profiles can differentiate post-COVID-19 condition from ME/CFS and fibromyalgia, suggesting these conditions involve different immunological mechanisms despite overlapping clinical presentations.
Viral triggers, particularly HERV-W ENV expression, may play a role in post-COVID-19 condition and potentially in prepandemic ME/CFS and fibromyalgia.
Objective blood-based biomarkers could provide a diagnostic tool to help clinicians differentiate between these overlapping syndromes and may point toward distinct therapeutic targets.
Remaining Questions
Do these blood biomarkers change over time during disease progression, or are they static markers? Prospective longitudinal studies are needed to clarify this.
What This Study Does Not Prove
This study does not establish whether the identified biomarkers are causative or merely correlated with disease status, nor does it prove these conditions have fundamentally different underlying mechanisms—only that their immune profiles differ measurably. The high specificity for post-COVID-19 condition does not necessarily apply to all patient populations, and findings require validation in prospective, longitudinal cohorts before clinical implementation.
Which specific biomarkers or biomarker combinations are most clinically useful for individual patient diagnosis, and how do results vary across diverse geographic and demographic populations?
Do the identified biomarkers have a causal role in symptom generation, or are they merely byproducts of disease processes?
Can biomarker-guided treatment approaches improve outcomes compared to symptom-based management in post-COVID-19 condition, ME/CFS, and fibromyalgia?