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What’s wrong in Psychological Medicine

In 2013, Psychological Medicine published a paper called “Recovery from chronic fatigue syndrome after treatments given in the PACE trial”, which claimed that 22% of patients had recovered in the CBT and GET groups.

In the paper, the PACE authors had abandoned all of the four criteria specified in the study protocol and had replaced them with far weaker ones.

The original recovery criteria for fatigue and physical function were explicitly replaced by the “normal ranges”, which were now called “thresholds of recovery”. Both overlapped the levels of severe fatigue and disability needed to enter the trial. The table below shows how drastic the change was to the original physical function recovery threshold.

SF-36 physical function scale

100 healthy physical function
85 or above original, discarded recovery threshold
65 or below disabled enough to enter the trial
60 or above new, “normal range” recovery threshold
0 most extreme disability

Concerning the third of the four recovery thresholds, the authors said:

“We considered scores of 1 (‘very much better’) or 2 (‘much better’) as evidence of the process of recovery, rather than our original protocol threshold of a score of 1 only, because we considered that participants rating their overall health as ‘much better’ represented the process of recovery.”

That is, the authors stated that this threshold no longer represented achieved, actual recovery but instead “the process of recovery” — that is, merely improvement — but they used it to define recovery in their new analysis.

The fourth threshold for recovery had originally been that patients should no longer fit any of the three clinical case definitions for CFS or ME used in the trial. But in the Psychological Medicine paper, all three of the case definitions now required patients to score 65 or worse on the physical function scale and 6 or worse on the fatigue scale in order to be considered “cases”. Adding these requirements made the case definitions harder to meet than in normal clinical practice and hence easier to “recover” from.

Thus a patient who would be diagnosed with CFS in the clinic and who was still extremely disabled with poor physical function would be considered recovered in the PACE trial if they had improved slightly on fatigue and scored 5 out of 11 at the end of the trial — which is a score that still represents considerable fatigue.

In an additional analysis, the authors considered patients to have achieved “trial recovery” if they had recovered according to the strengthened Oxford criteria but were still ill according to the other two case criteria. Even though such a “recovery” would clearly be meaningless, the recovery figures based on this analysis are those reported in the paper’s abstract.

Although the study authors said that they changed the recovery criteria before the analysis, the use of the “normal ranges” suggests that the changes were made after the study’s general results were known.

The journal published letters that criticised the new thresholds but no retraction of the recovery claims has been made.

We call upon Psychological Medicine to now retract these results.

 

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