The transfusion audit as a tool to improve transfusion practice: a critical appraisal.

Transfusion audits have a long history and they are required by many regulatory agencies. These audits have been touted as effective in reducing unnecessary transfusions as evidenced by many published articles on the subject. Most of these studies, however, have one or more flaws in their design including the use of historical controls, disregard of the Hawthorne effect, use of multiple interventions, and publication bias. Studies differ in the baseline rate of inappropriate transfusions and have different methods of measuring these rates. There is also little data on how long the effect of implementing a transfusion audit system may last. Transfusion audits appear most successful when there is a high baseline rate of inappropriate transfusions and interventions other than the audit itself are performed. Individual institutions should critically evaluate whether or not their current system of transfusion audits is useful.