Scaling the Tower of Babel. The impact of including foreign language articles in a large scale systematic review

Abstract

Ideally systematic reviews should include all relevant evidence to answer a given research question. However, in practice there is a trade-off between budgetary and time constraints and the inclusion of studies in languages other than English (LOE). 1 Current guidance recommends identifying papers in LOE and giving consideration as to whether language restrictions may bias the results of the review. 1 An issue which does not appear to have been fully considered is how excluding papers in LOE from systematic reviews might impact on the credibility of the review in the eyes of stakeholders. We were commissioned to conduct a systematic review of photodynamic therapy (PDT) for the treatment of pre-cancerous skin conditions, Barrett’s oesophagus and cancers of the biliary tract, brain, head and neck, lung, oesophagus and skin. 2 PDT is a controversial topic area, often generating polarised opinions. The team needed to demonstrate their commitment to an objective, thorough, unbiased review of all the relevant evidence