Where are the systematic reviews in transfusion medicine? A study of the transfusion evidence base.

Transfusion medicine has become a large and complex specialty. Although there are now systematic reviews covering many aspects of transfusion, these span a large number of clinical areas and are published across more than a hundred different medical journals, making it difficult for transfusion medicine practitioners and researchers to keep abreast of the current high-level evidence. In response to this problem, NHS Blood and Transplant's Systematic Review Initiative (SRI) has produced a comprehensive overview of systematic reviews in transfusion medicine. A systematic search (to December 2009) and screening procedure were followed by the appraisal of systematic reviews according to predefined inclusion criteria. The 340 eligible systematic reviews were mapped to 10 transfusion intervention groups and 14 topic groups within clinical medicine. Trends in the systematic review literature were examined and gaps in the literature described. The spread of systematic reviews across clinical areas was found to be very uneven, with some areas underreviewed and others with multiple systematic reviews on the same topic, making the identification of the best evidence for current transfusion practice a continuing challenge. References and links to all systematic reviews included in this overview can be freely accessed via the SRI's new online database, the Transfusion Evidence Library (www.transfusionguidelines.org).