Comment in Pub Med: Exploring changes to PACE trial outcome measures using anonymised data from the FINE trial, by Sam Carter, Feb 15 2016
When the results of the PACE trial were published (1, 2) it was noted that the primary outcome measures and the definition of “recovery” described in the trial’s published protocol (3) had been abandoned and replaced with markedly less stringent criteria.
The fully anonymised data set from the FINE trial(4), considered to be the PACE trial’s “sister” study, makes it possible to explore how these changes may have affected the reported efficacy of the PACE trial’s interventions.
At week 20 (assessment 2), 18 FINE trial participants met PACE trial post-hoc recovery thresholds (SF36 PF ≥ 60 and CFQ Likert ≤ 18) compared to only 3 participants who met the stricter, protocol-defined recovery thresholds (SF36 PF ≥ 85 and CFQ bimodal ≤ 3). Therefore, at assessment 2, the post-hoc changes increased the “recovery” rate by a factor of 6.
By week 70 (assessment 3), between 10 and 12 of the original 18 had relapsed so that they no longer met the post-hoc recovery thresholds (data are missing for two participants). Such a high rate of relapse within a year shows that the post-hoc recovery thresholds, said to represent a “strict criterion for recovery” in a Comment (5) which accompanied the original publication of PACE trial results, are neither strict nor reliable indicators of sustained wellbeing.
Regarding the Chalder fatigue questionnaire, White et al wrote that “we changed the original bimodal scoring of the Chalder fatigue questionnaire (range 0–11) to Likert scoring to more sensitively test our hypotheses of effectiveness” (1). However, data from the FINE trial show that Likert and bimodal scores are often contradictory and thus call into question White et al’s assumption that Likert scoring is necessarily more sensitive than bimodal scoring.
For example, of the 33 FINE trial participants who met the post-hoc PACE trial recovery threshold for fatigue at week 20 (Likert CFQ score ≤ 18), 10 had a bimodal CFQ score ≥ 6 so would still be fatigued enough to enter the PACE trial and 16 had a bimodal CFQ score ≥ 4 which is the accepted definition of abnormal fatigue.
Therefore, for this cohort, if a person met the PACE trial post-hoc recovery threshold for fatigue at week 20 they had approximately a 50% chance of still having abnormal levels of fatigue and a 30% chance of being fatigued enough to enter the PACE trial.
A further problem with the Chalder fatigue questionnaire is illustrated by the observation that the bimodal score and Likert score of 10 participants moved in opposite directions at consecutive assessments i.e. one scoring system showed improvement whilst the other showed deterioration.
Moreover, it can be seen that some FINE trial participants were confused by the wording of the questionnaire itself. For example, a healthy person should have a Likert score of 11 out of 33, yet 17 participants recorded a Likert CFQ score of 10 or less at some point (i.e. they reported less fatigue than a healthy person), and 5 participants recorded a Likert CFQ score of 0.
The discordance between Likert and bimodal scores and the marked increase in those meeting post-hoc recovery thresholds suggest that White et al’s deviation from their protocol-specified analysis is likely to have profoundly affected the reported efficacy of the PACE trial interventions.
An independent re-analysis of anonymised PACE trial data as described in its published protocol is urgently required to quantify the effects of the revised outcome and recovery criteria.
References
(1) White PD 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.
Lancet Mar 5;377(9768):823-36.
(2) White PD, Goldsmith K, Johnson AL, Chalder T, Sharpe M (2013) Recovery from chronic fatigue syndrome after treatments given in the PACE trial. Psychol Med. Oct;43(10):2227-35.
(3) White PD, Sharpe MC, Chalder T, DeCesare JC, Walwyn R (2007) Protocol for the PACE trial: a randomised controlled trial of adaptive pacing, cognitive behaviour therapy, and graded exercise, as supplements to standardised specialist medical care versus standardised specialist medical care alone for patients with the chronic fatigue syndrome/myalgic encephalomyelitis or encephalopathy.
BMC Neurol Mar 8;7:6.
(4) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4685991/bin/pone.0144623.s002.dta
(5) Bleijenberg G, Knoop H. (2011) Chronic fatigue syndrome: where to PACE from here? Lancet. Mar 5;377(9768):786-8.
