A method for diagnosing myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is provided in the present disclosure. The present disclosure provides a method that uses the B cell receptor (BCR) repertoire as an indicator of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). One or more variables selected from the group consisting of the frequency of use of one or more genes in the IgGH heavy chain variable region of the BCR in a subject, the BCR diversity index in a subject, and the level of one or more immune cell subpopulations in a subject can be used as an indicator of ME/CFS in the subject.

Provided herein are methods for treating complement-mediated diseases and associated conditions.

The application relates to a method for diagnosis of a chronic fatigue disease, e.g. CFS or CRF, comprising the step of determining the presence or absence of antibodies directed against -adrenergic receptor in a sample of the subject to be diagnosed, wherein the presence of antibodies directed against -adrenergic receptor is indicative of the chronic fatigue disease in said subject. Furthermore, the application relates to kits comprising -adrenergic receptor or an antigenic peptide thereof and the use of -adrenergic receptor or an antigenic peptide thereof for the diagnosis of a chronic fatigue disease.

Described herein are methods and devices for diagnosing chronic fatigue syndrome using peptide arrays, and providing a prognosis to patients.

The application relates to a method for diagnosis of a chronic fatigue disease, e.g. CFS or CRF, comprising the step of determining the presence or absence of antibodies directed against -adrenergic receptor in a sample of the subject to be diagnosed, wherein the presence of antibodies directed against -adrenergic receptor is indicative of the chronic fatigue disease in said subject. Furthermore, the application relates to kits comprising -adrenergic receptor or an antigenic peptide thereof and the use of -adrenergic receptor or an antigenic peptide thereof for the diagnosis of a chronic fatigue disease.

The present disclosure provides methods and kits using certain biomarkers in predicting and monitoring post-viral syndromes (for instance, chronic fatigue syndrome (CFS) and/or long CO VID), selectively treating such syndromes, and assessing clinical sensitivity and therapeutic response to treatments. Wherein determining an expression level of a biomarker in a sample from the subject is disclosed.