The national head and neck histopathology external quality assurance scheme: evolution, design, and analysis of 11 circulations from 1999 to 2005.

The background and design of a specialised head and neck histopathology external quality assurance (assessment) scheme with optional oral and ENT arms is described. Participation (submission of response forms) exceeded 85% in eight of 11 slide circulations. In 60% of the 168 circulated cases, up to 33% (and in occasional cases, up to 56%) of respondents gave incomplete or wrong responses owing to a lack of awareness of specific diagnostic entities or to the misinterpretation of specific histological features. In all, there were 118 wrong responses, of which 58% could be considered "potentially serious". The scheme incorporates several design features which optimise the educational value. The stringent marking of cases, and the flagging of performances showing "a meaningful deviation in standard" based on the decision of peer members rather than a rigid numerical formula, encourages high standards.