Quality assurance in breast cancer screening cytology: a review of the literature and a report on the U.K. national cytology scheme.

The National Breast Screening Programme in the United Kingdom has had an external quality assessment (EQA) scheme for breast screening histopathology since 1990. Recently, it was decided, by the Cytology sub-group of the National Co-ordinating Committee for Breast Screening Pathology, to institute two forms of cytology quality assurance. An EQA scheme is planned with circulation of slides to pathologists, but this involves extra time and effort from the participants at a time when general pathology workloads are high. Because of this, a computer routine has been written to analyse the data already present within the National Breast Screening Computer Systems, to enable the calculation of sensitivity and specificity of fine needle aspiration, correlating the cytology results with subsequent histology or follow-up mammography for lesions where no biopsy is performed. This routine uses standardised terminology and calculations and, therefore, inter-unit comparisons can be made. Where problems are identified within a unit, the Quality Assurance team can investigate the cause and institute appropriate measures to correct the problem. This article details the procedures involved in this audit and reviews the literature, recalculating the parameters in a standard manner for a number of publications. The results of the cytology quality assurance routine from seven screening units in one health region in the U.K. are presented and the measures taken to improve the level of service are discussed.