Fig. 5

Principal component analysis between self-reported outcome measures and endothelial and inflammatory status biomarkers in the study participants. Principal component analysis (PCA) biplot of individuals and explanatory variables for each cohort of participants for the first (X-axis) and second (Y-axis) principal components. The biplot shows PCA scores with 95% confidence ellipses for each cohort of outcome measure scores (A), symptom questionnaire scores plus endothelial biomarkers (B), outcome measure scores plus inflammatory biomarkers (C), and outcome measure scores plus biomarkers of endothelial function and inflammatory status (D) in individuals with ME/CFS, long COVID, and matched sedentary healthy controls. Colored concentration ellipses (size determined by a probability level at 0.95) show the observations grouped by mark class