The PACE Trial and Its Aftermath (2011-2021)
1 The Original PACE Trial
The PACE trial (Pacing, graded Activity, Cognitive behaviour therapy — a randomised Evaluation), published in The Lancet in 2011, was the largest ME/CFS treatment trial ever conducted (n=641) (White et al. 2011). It compared four arms: cognitive behavioral therapy (CBT), graded exercise therapy (GET), adaptive pacing therapy (APT), and specialist medical care (SMC) alone. The trial reported that CBT and GET were “moderately effective” with recovery rates of 22% in the CBT/GET arms (using the 2013 follow-up thresholds).
The trial’s methodological vulnerabilities became apparent through independent re-analysis. The most consequential: mid-trial changes to recovery thresholds. The original protocol defined “recovery” using an SF-36 physical function score ≥85 and a Chalder fatigue score ≤18 using bimodal scoring. The published paper lowered the threshold to SF-36 physical function ≥60 and Chalder fatigue ≤18 using Likert scoring — a substantial weakening of the recovery definition (Wilshire et al. 2018). Under the original protocol thresholds, recovery rates were approximately 6% in all groups, and CBT/GET showed no meaningful advantage (Vink 2015).
Additional concerns included: use of the Oxford criteria (which did not require PEM and permitted inclusion of patients with depression), unblinded design with subjective primary outcomes, and failure to report harms. Patient surveys conducted after the trial found that 54–74% of ME/CFS patients reported worsening from GET, directly contradicting the trial’s safety conclusions (Geraghty, Hann, and Kurtev 2019).
2 Institutional Reversals
The PACE controversy produced a series of institutional reversals unprecedented in modern medicine:
- 2017: The CDC removed graded exercise therapy and cognitive behavioral therapy as recommended treatments from its clinical guidance
- 2019: Cochrane withdrew its systematic review of exercise therapy for CFS, citing the need to apply current methodological standards; the revised review (Larun 2019) found low-certainty evidence of reduced fatigue from exercise but noted that findings may not apply to cohorts defined by PEM-requiring criteria
- 2021: NICE published guideline NG206, which explicitly recommends against graded exercise therapy and states that CBT should be offered as supportive therapy only — not as a curative treatment (National Institute for Health and Care Excellence 2021)
This pattern — a high-profile trial published in a top-tier journal, followed by independent re-analysis exposing methodological vulnerabilities, followed by institutional reversal — has made the PACE trial the single most-cited cautionary tale in ME/CFS research methodology. The episode also demonstrated the epistemic function of patient advocacy: it was patient-led FOIA requests and independent statisticians that forced data release and re-analysis, not institutional quality control. Patient-Generated Knowledge and Citizen Science provides a systematic treatment of patient communities as epistemic correction mechanisms.
3 NICE 2021 Guideline
The NICE 2021 guideline (NG206) represented a methodological and clinical departure from previous UK guidance (National Institute for Health and Care Excellence 2021). Using GRADE methodology, NICE reviewed the entire evidence base and concluded that graded exercise therapy should not be offered, that CBT should only be offered as supportive therapy, and that energy management (pacing) is the appropriate self-management strategy. The guideline established four core symptoms required for diagnosis: debilitating fatigue, PEM, unrefreshing sleep, and cognitive difficulties. The three-month minimum duration was shorter than the Fukuda six-month requirement, reflecting concern that delayed diagnosis causes harm.