Investigating the factors associated with meaningful improvement on the SF-36-PFS and exploring the appropriateness of this measure for young people with ME/CFS accessing an NHS specialist service: a prospective cohort study.

40% and 54% of young people reached the MCID at 6 and 12 months, respectively. No factors at assessment (other than SF-36-PFS at 6 months, and pain and SF-36-PFS at 12 months) are associated with MCID of SF-36-PFS at either 6 or 12 months. Further work is needed to explore the most appropriate outcome measure for capturing clinical meaningful improvement for young people with ME/CFS.