Castro-Marrero, Jesús, Zacares, Mario, Almenar-Pérez, Eloy et al. · Journal of clinical medicine · 2021 · DOI
Researchers analyzed blood samples from 250 women with ME/CFS to see if specific blood markers could help identify different types of the disease. They found that about 43% of participants had high levels of a protein called C1q, which was particularly associated with those experiencing more pain symptoms. This discovery suggests that blood tests might one day help doctors identify which ME/CFS patients belong to which subgroup, potentially leading to better tailored treatments.
ME/CFS currently lacks objective diagnostic tests and relies entirely on clinical symptoms, making diagnosis challenging and variable across providers. Identifying blood-based markers like C1q could enable earlier, more accurate diagnosis and reveal disease subtypes that might respond differently to treatments. This work provides a foundation for developing laboratory tests that could revolutionize ME/CFS clinical management and accelerate targeted research.
This study does not prove that C1q causes ME/CFS or pain symptoms—it only shows an association in this cross-sectional snapshot. The findings are specific to women and cannot be assumed to apply to men with ME/CFS. The study does not establish whether C1q elevation is a consequence of ME/CFS, a contributing factor, or an unrelated marker in a subgroup.
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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