BMJ  2006;333:916 (28 October), doi:10.1136/bmj.333.7574.916

Letter

Cochrane reviews v industry supported meta-analyses

We should read all reviews with caution

EDITOR—That industry sponsored meta-analyses differ in conclusions from Cochrane reviews does not mean that industry sponsorship is the only source of bias or that Cochrane reviews should be uncritically accepted.¹

Allegiances of authors of meta-analyses are not only associated with selective attention to relevant studies and more positive conclusions in the case of industry ties.² We should be sceptical about a comparative review from the director of a Cochrane Centre that puts the centre in such a favourable light.

Credit: GUSTO/SPL

 

Cochrane reviews are sometimes conducted on literature that is not ready for meta-analysis, with adverse implications for clinical practice and public policy. A recent Cochrane meta-analysis concluded that couples therapy was not better than individual therapy for depression.³ The offering of couples therapy should be a matter of "patient preference and availability of specific resources." Yet, the studies reviewed were all seriously flawed. None had close to the minimal cell size necessary for inclusion in a meta-analysis, much less for a nonequivalence trial. Such a premature conclusion serves to discourage the commitment of scarce resources to having marital therapists available or to research providing an adequate comparison between the two forms of therapy.

Whether the Cochrane Collaboration is free of bias should not be left to the collaboration to decide. Bjordal et al showed that only investigators associated with negative findings had been recruited to the review group for a Cochrane report on low level laser therapy in osteoarthritis.⁴ The review had numerous deficiencies in ways consistently supporting its negative conclusion.

The Cochrane Collaboration describes itself as "the gold standard in evidence-based healthcare" (www3.interscience.wiley.com/cgi-bin/mrwhome/106568753/HOME).

The paragraph in This week in the BMJ for the paper by Jørgensen et al admonished us to "Read industry supported drug reviews with caution." This should be expanded to all reviews, including those of the Cochrane Collaboration.

University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA jcoyne{at}mail.med.upenn.edu

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Competing interests: None declared.

References

1. Jørgensen AW, Hilden J, Gøtzsche PC. Cochrane reviews compared with industry supported meta-analyses and other meta-analyses of the same drugs: systematic review. BMJ 2006;333: 782-5. (14 October.)[Abstract/Free Full Text]
2. Parker G, Roy K, Eyers K. Cognitive behavior therapy for depression? Choose horses for courses. Am J Psychiatry 2003;160: 825-34.[Abstract/Free Full Text]
3. Barbato A, D'Avanzo B. Marital therapy for depression. Cochrane Database Syst Rev. 2006; (2): CD004188.pub2.
4. Bjordal JM, Lopes-Martins RAB, Klovning A. Is quality control of Cochrane reviews in controversial areas sufficient? Journal of Alternative and Complementary Medicine 2006;12: 181-3.[CrossRef][ISI][Medline]

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