Methods: All systematic reviews relevant to transfusion medicine have been identified. The principle source was The Cochrane Library 2004. Overviews of systematic reviews focusing on the areas of transfusion practice identified by the "Handbook of Transfusion" have been conducted over the past two years. The problems arising have been documented. The validity of the observations will be tested on experienced reviewers not part of the original overview team, who will be challenged with the same collections of reviews. Consensus about possible ways to overcome problems will also be examined.

Results: Five overviews have been completed, each containing over 15 systematic reviews; validation of problems and potential solutions arising from these is in progress. An interesting emergent issue concerned limitations associated with question definition, an area on which Cochrane reviews have placed considerable emphasis. Exploring this in depth will be a priority.

Conclusions: Validation will be complete by October 2006.