Measures of symptoms and disease severity
The severity of ME/CFS was categorized into five groups (mild, mild-moderate, moderate, moderate/severe, severe). The categorization into different severity groups was based on thorough clinical assessment by the physician at the time of inclusion, and supported by patient-reported function level and questionnaires. Self-reported questionnaires at baseline included the Short-Form-36 Health Survey (SF-36) (version 1.2) [