Are external quality assurance (EQA) slide schemes a valid tool for the performance assessment of histopathologists?

Quality assurance plays a vital role in the healthcare profession and histopathologists play a central role in the diagnosis and treatment of disease. In the past these specialists have worked in isolation and quality assurance of their work has been difficult. In recent years this has changed with the introduction of External Quality Assurance slide schemes. This paper discusses how these schemes have evolved, the problems of standard setting and their validity as a measure of pathologists performance.