Functional Capacity Assessment in ME/CFS (FUNCAP)
1 Sommerfelt et al. 2024 — FUNCAP: Patient-Informed Functional Capacity Questionnaire
Full Citation:: Sommerfelt K, Schei T, Seton KA, Carding SR. Assessing Functional Capacity in Myalgic Encephalopathy/Chronic Fatigue Syndrome: A Patient-Informed Questionnaire. Journal of Clinical Medicine. 2024;13(12):3486. DOI:: 10.3390/jcm13123486 PMID:: 38930014 PMCID:: PMC11204454 Study Design:: Questionnaire development and validation (5 rounds of web surveys + test-retest) Sample Size:: Norwegian sample n=1,263 ME/CFS + 178 HC; international English sample n=1,387 ME/CFS Key Findings::
- Developed FUNCAP55 (55 items) and FUNCAP27 (27 items) questionnaire versions
- 8 domains: personal hygiene, walking/movement, being upright, home activities, communication, activities outside home, light/sound reactions, concentration
- Novel question design: asks about *consequences* of activity, not whether patient "can" do it
- Good reliability and validity; negligible floor/ceiling effects
- Discriminates ME/CFS severity levels (mild to very severe)
- Validated in two independent large samples (Norwegian + international English)
- Available in 8 languages (Dutch, English, French, German, Italian, Japanese, Norwegian, Swedish)
- CC BY license — free to use for clinical and research purposesConclusion:: FUNCAP is the first patient-informed functional capacity questionnaire specifically designed for PEM-affected patients. It addresses a critical gap in ME/CFS assessment for diagnosis, follow-up, disability evaluation, and research. Limitations:: Cross-sectional validation only (no longitudinal sensitivity-to-change data yet); single-center development; no independent external validation study published as of 2026; JCM is a mid-tier MDPI journal. Certainty:: 0.70
2 Weigel et al. 2024 — Symptom Clusters and Patient-Reported Outcomes in ME/CFS and PCC
Full Citation:: Weigel B, Eaton-Fitch N, Thapaliya K, Marshall-Gradisnik S. A pilot cross-sectional investigation of symptom clusters and associations with patient-reported outcomes in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Post COVID-19 Condition. Quality of Life Research. 2024;33(12):3229–3243. DOI:: 10.1007/s11136-024-03794-x PMID:: 39361124 PMCID:: PMC11599292 Study Design:: Pilot cross-sectional Sample Size:: ME/CFS n=60, PCC n=30 (Australian residents) Key Findings::
- Autonomic symptoms (notably dyspnoea) associated with poorest patient-reported outcomes across both cohorts
- No symptom clusters unique to ME/CFS or PCC — clusters delineated by GI/neurosensory symptoms, illness duration, criteria met
- Pain, flu-like symptoms, and temperature dysregulation more burdensome in PCC (possibly representing early-stage ME/CFS)
- Illness duration may explain differences in symptom burden between ME/CFS and PCCRelevance to FUNCAP:: Demonstrates need for tools like FUNCAP that capture functional capacity across PEM-affected populations (ME/CFS and PCC). Validates the construct that functional capacity is central to both conditions. Limitations:: Small sample (n=90 total); single center; cross-sectional; no use of FUNCAP itself Certainty:: 0.50
3 Jason & Chee 2025 — Brief Comprehensive Measure of Post-Exertional Malaise
Full Citation:: Jason LA, Chee KJ. A brief, comprehensive measure of post-exertional malaise. Exploration of Neuroprotective Therapy. 2025. DOI:: 10.37349/ent.2025.1004116 Study Design:: Questionnaire development Key Findings::
- Develops a brief PEM measure complementing existing functional capacity tools
- Cites FUNCAP as validating that functional capacity has been "well assessed" in ME/CFS
- Addresses physical fatigue, reduced stamina/functional capacity as core PEM symptomsRelevance to FUNCAP:: Complementary PEM measurement tool; references FUNCAP as the standard for functional capacity assessment in ME/CFS Limitations:: New instrument without extensive validation data; small journal (Exploration of Neuroprotective Therapy) Certainty:: 0.50
4 Goxhaj et al. 2026 — Negative Results in Long COVID Trials: Outcome Measures
Full Citation:: Goxhaj L, McCorkell L, van Rhijn-Brouwer F, Soares L, Vogel JM, de Canson C. Negative results in long COVID clinical trials: choosing outcome measures for a heterogeneous disease. Lancet Infectious Diseases. 2026;26(1):13–15. DOI:: 10.1016/S1473-3099(25)00665-6 PMID:: 41213281 Study Design:: Commentary/Editorial Key Findings::
- Argues that poor outcome measure choice drives negative results in Long COVID trials
- Highlights FUNCAP as a functional capacity scale specifically designed for PEM-affected patients
- Emphasizes need for measures capturing the activity-limiting nature of ME/CFS
- Patient-led research collaborative authorshipRelevance to FUNCAP:: Lancet Infectious Diseases commentary recommending FUNCAP as a functional capacity outcome measure for PEM-related conditions — significant endorsement in a top-tier journal Limitations:: Commentary, not original research; no new data Certainty:: 0.40
5 Meadows et al. 2025 — LIFT Trial Protocol (FUNCAP-55 as Primary Outcome)
Full Citation:: Meadows D, Squires J, Dibble J, Palwayi S, et al. Pyridostigmine and low-dose naltrexone for ME/CFS: study protocol for the Life Improvement Trial (LIFT), a randomized, double-blind, placebo-controlled clinical trial. Research Square (preprint). 2025. DOI:: 10.21203/rs.3.rs-5626167 Study Design:: RCT protocol (preprint) Key Findings::
- FUNCAP-55 score designated as primary outcome measure
- Also measures peak VO~2~ and heart rate variability
- Tests combination of pyridostigmine + LDN for ME/CFSRelevance to FUNCAP:: First RCT to adopt FUNCAP-55 as primary outcome — validates its suitability as an interventional trial endpoint Limitations:: Preprint only (not peer-reviewed); protocol stage — no results yet Certainty:: 0.30