Blood parameters differentiate post COVID-19 condition from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia

Abstract:

Post-COVID-19 condition, such as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Fibromyalgia (FM), are characterized by fatigue, pain, shortness of breath, sleep disturbances, cognitive dysfunction and other symptoms, heavily impacting on patients daily functioning. Moreover, over half of patients end up fulfilling ME/CFS and/or FM clinical criteria after a few months of SARS-CoV-2 infection.

Expression of the toxic human endogenous retrovirus (HERV)-W ENV protein can be induced by viral infection and HERV-W detection was correlated with acute COVID-19 severity and found significantly expressed in post-COVID-19 condition. This study shows that HERV-W ENV may also be present in prepandemic cases of ME/CFS, FM or co-diagnosed with both clinical criteria, suggesting viral participation in these chronic diseases.

To learn whether associated antiviral mechanisms may also show differing patterns of immunological responses, we measured IgM, IgG, IgA and IgE antibody isotypes against SARS-CoV-2 spike and nucleocapsid antigens, the levels of IL-6, IL-8, IL-10, IFNγ and TNFα cytokines, the level of NfL, a neural damage biomarker, as well as some blood cell markers potentially related with fatigue.

Importantly, some of the measured variables showed a capacity to discriminate post-COVID-19 condition cases from all other participants, with 100 % sensitivity and up to 71.9 % specificity providing a new tool for a differential diagnosis between diseases or syndromes with so many overlapping clinical symptoms. Interestingly, the detected markers showed moderate-to-strong correlations with patient symptoms pointing at novel therapeutic opportunities.

Source: Giménez-Orenga K, Pierquin J, Brunel J, Charvet B, Martín-Martínez E, Lemarinier M, Fried S, Lucas A, Perron H, Oltra E. Blood parameters differentiate post COVID-19 condition from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia. Brain Behav Immun Health. 2025 Jul 4;48:101058. doi: 10.1016/j.bbih.2025.101058. PMID: 40726775; PMCID: PMC12302357. https://pmc.ncbi.nlm.nih.gov/articles/PMC12302357/ (Full text)

IgE levels are the same in chronic fatigue syndrome (CFS) and control subjects when stratified by allergy skin test results and rhinitis types

Abstract:

BACKGROUND: Chronic fatigue syndrome (CFS) has an uncertain pathogenesis. Allergies have been suggested as one cause.

OBJECTIVE: The aim of this study was to compare serum immunoglobulin (Ig)E in CFS and control subjects to determine whether IgE levels were elevated in CFS. This would be suggestive of increased atopy in CFS.

METHODS: IgE was measured by quantitative ELISA (sandwich) immunoassay in 95 CFS and 109 non-CFS control subjects. Subjects were classified by positive or negative allergy skin tests (AST) and rhinitis questionnaires (rhinitis score, RhSc) into four rhinitis types: nonallergic rhinitis (NAR with positive RhSc and negative AST); allergic rhinitis (AR with positive AST and RhSc); atopic/no rhinitis (AST positive/RhSc negative); and nonatopic/no rhinitis (both AST and RhSc negative) subjects.

RESULTS: IgE was not significantly different between control (128 +/- 18 IU/mL, mean +/- SEM) and CFS (133 +/- 43 IU/mL) groups, or between control and CFS groups classified into the four rhinitis types. IgE was significantly higher in subjects with positive AST whether or not they had positive RhSc or CFS symptoms.

CONCLUSIONS: Elevated IgE and positive AST indicate allergen sensitization, but are not necessarily indicators of symptomatic allergic diseases. There was no association between IgE levels and CFS, indicating that atopy was probably not more prevalent in CFS. Therefore, TH2-lymphocyte and IgE-mast cell mechanisms are unlikely causes of CFS.

 

Source: Repka-Ramirez MS, Naranch K, Park YJ, Velarde A, Clauw D, Baraniuk JN. IgE levels are the same in chronic fatigue syndrome (CFS) and control subjects when stratified by allergy skin test results and rhinitis types. Ann Allergy Asthma Immunol. 2001 Sep;87(3):218-21. http://www.ncbi.nlm.nih.gov/pubmed/11570618

 

Chronic fatigue syndrome–a controlled cross-sectional study

Abstract:

Twenty-one patients fulfilling the Center for Disease Control criteria for chronic fatigue syndrome (CFS) were examined in a controlled study. Viral antibodies and tests evaluating the immune system were investigated in the patients and in a control group of 21 sex- and age-matched individuals.

Production in vitro of the predominantly T-cell-derived cytokines interleukin-2 and interferon-gamma was significantly higher in patients with CFS compared the control group. Furthermore, the serum concentrations of IgA and IgE were significantly lower in patients with CFS; however, the values were within the normal reference range.

All other variables were similar in the two groups. This study does not suggest a clearly disordered immune system or a chronic viral infection as a major pathogenetic factor in CFS. Longitudinal studies of immunological and virological parameters in CFS are warranted as are studies on patients that are severely handicapped.

Comment in: [Chronic fatigue syndrome and angiotensin-converting enzyme]. [Ugeskr Laeger. 1995]

 

Source: Rasmussen AK, Nielsen H, Andersen V, Barington T, Bendtzen K, Hansen MB, Nielsen L, Pedersen BK, Wiik A. Chronic fatigue syndrome–a controlled cross-sectional study. Ugeskr Laeger. 1994 Nov 14;156(46):6836-40. [Article in Danish] http://www.ncbi.nlm.nih.gov/pubmed/7839498

 

Chronic fatigue syndrome–a controlled cross sectional study

Abstract:

OBJECTIVE: To look for signs of immunodeficiencies and/or longstanding infections underlying chronic fatigue syndrome (CFS).

METHODS: Twenty-one patients fulfilling the Centers for Disease Control criteria for CFS were compared to 21 age and sex matched controls. A number of viral antibodies as well as the following tests evaluating the immune system were studied: autoantibody profile, cell surface markers on isolated blood mononuclear cells, cytokine production, lymphocyte proliferative responses, natural killer cell activity and quantitation of immunoglobulin secreting cells.

RESULTS: Production in vitro of the predominantly T cell derived cytokines interleukin 2 and interferon gamma was significantly higher in patients with CFS compared to the control group. Furthermore, the serum concentrations of IgA and IgE were lower in patients with CFS; however, this difference was caused by a larger number with values of IgA and IgE above the upper limit of the normal range among the controls than among the patients with CFS. All other variables were similar in the 2 groups.

CONCLUSION: A pathogenically significant imbalance of the immune system in patients with CFS cannot be excluded. However, evidence of a causal link between abnormal immunity and CFS was not obtained.

 

Source: Rasmussen AK, Nielsen H, Andersen V, Barington T, Bendtzen K, Hansen MB, Nielsen L, Pedersen BK, Wiik A. J Rheumatol. 1994 Aug;21(8):1527-31. http://www.ncbi.nlm.nih.gov/pubmed/7983659