Doctor

Question marks over evidential basis of claims (correspondence)

Author

Abbot NC

Institution

MERGE, Perth, UK

Correspondence

Sharpe and Wilks’ review (1) contains an “evidence-based summary” with the statement, “graded exercise and cognitive behavioural therapies are effective in treating chronic fatigue syndrome.” However, rigorous examination of the literature indicates that this remark is not itself evidence-based, a serious criticism since evidence-based summaries in the BMJ carry weight and are widely quoted.

For the record, two research groups have now conducted systematic reviews of putative treatments for chronic fatigue syndrome (2, 3). They have identified 3 eligible randomised controlled trials (RCTs) of graded exercise therapy (GET) and 5 RCTs of cognitive behavioural therapy (CBT).

The total number of available trials is small, numbers are relatively low (6/8 trials have less than 40 subjects in the active groups), and two of the 5 CBT trials do not show an overall significant effect (see Table on BMJ website). No trial contains a ‘control’ intervention adequate to determine specific ‘efficacy’: in only 2 trials are the treatment arms compared with an ‘active’, though not indistinguishable, intervention. Yet, the chart in the clinical review (1) refers to the ‘efficacy’ of CBT, showing data from one trial (Prins et al, 2001) in which the comparison groups were guided support (social worker) for 11 sessions (against 16 sessions of CBT) and no intervention. A number of non-specific effects could have accounted for these results, and the fact that the drop-out rate in the active arm was 40% may point in this direction, as discussed in one of the reviews (2). Again, the heterogeneity of the trials, the potential effect of publication or funding bias for which there is some evidence (4), and professional doubts about the evidence base for some behavioural therapies themselves (5) give grounds for caution. Indeed, if a similar evidence base existed for, say, Shamanic healing — which has no professional proponents — it would arouse little clinical interest.

Neither of the review groups has commended GET or CBT as particularly effective for chronic fatigue syndrome patients. Whiting et al (2) state, “all conclusions about effectiveness should be considered together with the methodological inadequacies of the studies. Interventions that have shown promising results include CBT and GET”; and Mulrow et al (3) state, “…it is unlikely that the beneficial effects of such general treatments are specific or limited only to patients with CFS. In other words, although these therapies may help some people with CFS, their effectiveness does not help establish an underlying aetiology or cause of CFS.”

References

  1. Sharpe M, Wilks D. Fatigue. ABC of Psychological Medicine. BMJ 2002; 325: 480–3.
  2. Whiting P, Bagnall A-M, Sowden AJ et al. Interventions for the treatment and management of chronic fatigue syndrome: a systematic review. Journal of the American Medical Association 2001; 286: 1360–8.
  3. Mulrow CD, Ramirez G, Cornell JE et al. Defining and Managing Chronic Fatigue Syndrome. Evidence Report/Technology Assessment No. 42. AHRQ Publication No. 02-E001. Rockville (MD): Agency for Healthcare Research and Quality: October 2001.Available from www.ahrq.gov
  4. Abbot NC, Spence VA. Research into ME/CFS in the United Kingdom: Can the National Research Register inform future policy? ME Research UK analysis No. 01-M002. February 2002. Available from www.meresearch.org.uk
  5. Bolsover N. Commentary: The evidence is weaker than claimed. BMJ 2002; 384: 294.

Publication

British Medical Journal, 2002 Sep 17; online edition

Comment by ME Research UK

In response to an article in the British Medical Journal, we reviewed trials of the use of psychosocial therapies in ME/CFS. The total number of available trials is small, numbers are relatively low (6/8 trials have less than 40 subjects in the active groups), and 2 of the 5 cognitive behavioural therapy (CBT) trials do not show an overall significant effect. No trial contains a ‘control’ intervention adequate to determine specific ‘efficacy’: in only 2 trials are the treatment arms compared with an ‘active’, though not indistinguishable, intervention. A number of non-specific effects could have accounted for the positive results, and the fact that the drop-out rate in the active arm of one of the trials was 40% may point in this direction, as discussed in one of the reviews. Again, the heterogeneity of the trials, the potential effect of publication or funding bias for which there is some evidence, and professional doubts about the evidence base for some behavioural therapies themselves give grounds for caution.

Neither of the review groups has commended graded exercise therapy (GET) or CBT as particularly effective for chronic fatigue syndrome patients. Whiting et al state, “…all conclusions about effectiveness should be considered together with the methodological inadequacies of the studies. Interventions that have shown promising results include CBT andGET”; and Mulrow et al state, “…it is unlikely that the beneficial effects of such general treatments are specific or limited only to patients with CFS. In other words, although these therapies may help some people with CFS, their effectiveness does not help establish an underlying aetiology or cause of CFS.”

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