Dear Editor,

I read with interest the article on the Cochrane Collaboration's tool for assessing risk of bias by Higgins et al. I am an academic foundation year two doctor working with a Cochrane review group based at the University of York. My role within the team has been to help update Cochrane reviews, adding new studies identified since the review was last published, and to make sure the review meets the current Cochrane Collaboration standards. One of the main aspects of this role was to complete the new risk of bias assessment for all the studies in the review update comprising those included before the development of the new tool. The following is a brief summary of my experiences of assessing risk of bias using the Cochrane Collaboration tool.

Initially, the task of updating Cochrane reviews was a daunting one and I had a lot to learn. I found the Cochrane Handbook1 very helpful and was well supported by the excellent team at the editorial base. For me, the main positive aspect of the risk of bias tool is its ease of use and transparency. The Cochrane Handbook1 gives very clear instructions on how to use the tool and within RevMan (Cochrane's software package) the risk of bias tables are generated and summary figures produced automatically. The process of completing the risk of bias tables is also straightforward, as every decision made by the review authors must be supported by a quote from the study text. This requirement makes the decision making process transparent and allows the reader of the review to see how the judgement of bias was supported. Finally, the summary diagrams give a clear overview of, not only each individual study's risk of bias, but of the review as a whole.

I feel I have learnt a great deal in my short time working with the review group. I quickly learnt about the different types of bias, why they are important and how to detect them within the included studies of a Cochrane review. I have acquired a valuable skill, now being able to thoroughly appraise studies and assess their potential biases. I have a better understanding of how studies should be designed and importantly what information authors should report in the study publication to enable readers to detect any potential biases and be able to form a judgement on the evidence presented. I feel these skills are essential for all doctors in order to assess the medical literature upon which their clinical decision making is based.

1. Higgins JPT, Green S, eds. Cochrane handbook for systematic reviews of interventions. Wiley, 2008.