Functional Assessments

1 SF-36 (Short Form Health Survey)

The SF-36 is a generic health-related quality of life instrument widely used across chronic diseases, providing a benchmark for comparing ME/CFS functional impact with other conditions (Kingdon et al. 2018).

  • Purpose: Assessment of health-related quality of life across eight domains; comparison with population norms and other chronic disease groups.
  • Domains: Physical Functioning (PF), Role-Physical (RP), Bodily Pain (BP), General Health (GH), Vitality (VT), Social Functioning (SF), Role-Emotional (RE), Mental Health (MH).
  • Scoring: Each domain is scored 0–100, with higher scores indicating better health. Summary scores: Physical Component Summary (PCS) and Mental Component Summary (MCS).
  • ME/CFS-specific findings: ME/CFS patients score significantly lower than population norms on all domains, with the most severe impairment in RP, PF, SF, and VT. ME/CFS SF-36 scores are comparable to or lower than scores for congestive heart failure, multiple sclerosis, and type 2 diabetes (Kingdon et al. 2018) (Hvidberg et al. 2015).
  • Limitations: Generic instrument not designed for ME/CFS; does not capture PEM, orthostatic intolerance, or cognitive symptoms specifically; ceiling effects may limit sensitivity in severely affected patients who are unable to complete the questionnaire.

2 Chalder Fatigue Scale

The Chalder Fatigue Scale is an 11-item self-report measure of fatigue severity.

  • Purpose: Quantification of physical and mental fatigue severity.
  • Scoring: 11 items scored on a 4-point Likert scale (bimodal scoring: 0, 0, 1, 1) or a 4-point continuous scale (0–3). Total score ranges from 0 to 11 (bimodal) or 0 to 33 (Likert).
  • Limitations: Developed as a general fatigue measure, not specific to ME/CFS. Does not distinguish ME/CFS-type fatigue from fatigue due to depression, sleep disorders, or other causes. Used as a primary outcome in the controversial PACE trial (White et al. 2011), which has been criticized for using recovery thresholds that overlapped with entry criteria (Geraghty and Blease 2019). Not recommended as a sole outcome measure in ME/CFS trials.

References

Geraghty, Keith J, and Charlotte Blease. 2019. “Cognitive Dysfunction in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Review of Recent Evidence.” Current Rheumatology Reports 21 (9): 48. https://doi.org/10.1007/s11926-019-0848-z.
Hvidberg, Michael Falk, Louise Schouborg Brinth, Anne V Olesen, Karin D Petersen, and Lars Ehlers. 2015. “The Health-Related Quality of Life for Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).” PLOS ONE 10 (7): e0132421. https://doi.org/10.1371/journal.pone.0132421.
Kingdon, Caroline C, Erin A Bowman, Monica Curran, Luis Nacul, and Eliana Lacerda. 2018. “Functional Status and Well-Being in People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Compared with People with Multiple Sclerosis and Healthy Controls.” PharmacoEconomics - Open 2 (3): 281–92. https://doi.org/10.1007/s41669-018-0071-6.
White, Peter D, Kimberly A Goldsmith, Anthony L Johnson, Laura Potts, Rebecca Walwyn, Julia C DeCesare, Harriet L Baber, et al. 2011. “Comparison of Adaptive Pacing Therapy, Cognitive Behaviour Therapy, Graded Exercise Therapy, and Specialist Medical Care for Chronic Fatigue Syndrome (PACE): A Randomised Trial.” The Lancet 377 (9768): 823–36. https://doi.org/10.1016/S0140-6736(11)60096-2.