Letters

Cochrane reviews will be in Medline

EDITORErny and Maradit-Kremers (and the editor in his reply to their letter) note some difficulties caused by the fact that Cochrane reviews are not indexed in Medline.¹ This has made it difficult for people to identify these maintained systematic reviews and to keep track of them. We agree that this is a problem for anyone wishing to have access to up to date evidence of the effects of different healthcare interventions. Fortunately, this is set to change shortly as Cochrane reviews will soon be indexed in Medline. In addition, whenever a Cochrane review is updated substantively a record for the new version will be added to Medline with a reference to the earlier record.

In connection with this we are working within the Cochrane Collaboration to ensure that the impact of any updating of a Cochrane review is more transparent when the revised version is published in the Cochrane Library.² It would be helpful if all systematic reviewers could ensure that they inform readers if their review has been published elsewhere. This is already the case with Cochrane reviews, where details are given of other published versions within each review.

We would encourage anyone preparing guidelines for the reporting of systematic reviews to urge that reviewers are explicit about the existence of other versions. We have struggled for some time with the problems caused by the multiple publication of randomised trials without appropriate cross referencing³; as reviewers we should ensure that we do not set the same traps for users of our research.

It would be helpful if journals could develop a mechanism by which readers are made aware of updated versions of any research that the journals have published. The advent of electronic forms of the journals will facilitate this. It needs to be made much easier for readers and users of medical research to identify the most up to date description and findings of that research.

Mike Clarke, associate director (research). 
UK Cochrane Centre, Oxford OX2 7LG mclarke{at}cochrane.co.uk

Andy Oxman, chair, Cochrane Collaboration Steering Group. 
Health Services Research Unit, National Institute of Public Health, Postboks 4404 Torshov, Oslo N-0403, Norway