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EDUCATION AND DEBATE:
Heather E Elphick, Anton Tan, Deborah Ashby, and Rosalind L Smyth
Systematic reviews and lifelong diseases
BMJ 2002; 325: 381-384 [Full text]
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[Read Rapid Response] Systematic reviews of observational studies
Mohamed Farouk Allam   (22 August 2002)

Systematic reviews of observational studies 22 August 2002
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Mohamed Farouk Allam,
Research Fellow
Preventive Medicine and Public Health Department, Cordoba University, Cordoba 14004 Spain

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Re: Systematic reviews of observational studies

Elphick and his colleges [1] raised concerns about the value of pooling randomised controlled clinical trials of antibiotics therapy in cystic fibrosis. Methodological concerns included limitations in the quality of the primary data, as the usefulness of meta-analysis is largely depends on the quality of the studies that are synthesised.

It is surprising that nearly all systematic reviews, including Cochrane Collaboration reviews, concentrate on clinical trials. Little attention has been withdrawn towards the importance of pooling observational studies as cohort, case-control and ecological investigations.

Combining randomised controlled trials may provide more evidence; however combining data from observational studies is sometimes desirable, especially in studying the treatment of a chronic disease as in the case of cystic fibrosis. In addition, identification of chronic diseases risk factors is currently the most crucial problem in the epidemiology of non- infectious diseases and calls for pooling the results of dispersed observational studies.

I think that it is time to change the old concept that experimental studies are better than observational studies. The question is: Could we see, in the near future, an international collaboration as Cochrane Collaboration for pooling observational studies?

References:

1. Elphick HE, Anton T, Ashby D, Smyth RL. Systematic reviews and lifelong diseases. BMJ 2002;325:381-384.