Table 1 Definitions of improvement and recovery specified in the trial protocol [1], and those used in the final trial reports [2, 4]. Improvement was the primary outcome measure specified in the protocol. Recovery was a secondary measure

Overall Improvement

Minimum score of 75 on the 100-point SF-36 physical function scale or a score increase of 50% or more.

At least an 8 point increase in the 100-point SF-36 physical function scale.

Of the 11 fatigue items on the Chalder Fatigue Questionnaire (CFQ), three or fewer rated as worse/much worse than prior to illness OR the total items rated worse/much worse dropped by at least a 50%.

At least a 2 point decrease on the 33-point CFQ (Likert scoring method).

Recovery

Minimum score of 85 on the 100-point SF-36 physical function scale.

Minimum score of 60 on the 100-point SF-36 physical function scale.

Of the 11 items on the CFQ, three or fewer rated as worse/much worse than prior to illness.

Maximum score of 18 on the 33-point CFQ.

Overall health self-rated as “very much better” on the Clinical Global Impression scale [50].

Overall health self-rated as “much better” or “very much better” on the Clinical Global Impression scale.

The final “caseness” criterion was met if the patient no longer fulfilled: The Oxford case definition of CFS; the CDC criteria [51]; AND the London ME criteria [52]. (As determined by a non-blinded assessor).

The revised “caseness” criterion was met if ANY of the following applied: a) the patient did not meet the standard Oxford case definition; OR b) on the CFQ, they rated less than six of the 11 fatigue items as being worse than prior to illness; OR c) their SF-36 Physical Function score was greater than 65.