West Midlands screening histories project: methodology and use as an audit tool

The Screening Histories Project aims to assign a screening status classification to all primary breast cancers in women aged 50–64, who were diagnosed in the West Midlands from 1 March 1988 to 31 March 2001. The possible classifications are: screen detected, interval cancer, nonattender, lapsed attender and diagnosed before invite.

To obtain a screening status, screen-detected cancers are downloaded from the National Breast Screening Computer System (NBSS), matched against the West Midlands Cancer Intelligence Unit's cancer registration database, and classified as screen detected. All other eligible cases from the cancer registration database are manually checked against the NBSS. This involves assigning each case a screening unit and printing individual classification forms. The screening status is dependent upon whether the woman was invited prior to diagnosis and whether she attended her invitations.

The first project phase is complete and all women diagnosed up to 31 March 1998 have been assigned a screening history. Thirty-seven per cent of women had a screen-detected cancer, 22% were interval cancers, 14% were diagnosed before invite, 11% were nonattenders and 2% were lapsed attenders.

The dataset obtained by applying this algorithm is a valuable resource for the evaluation of breast screening in the West Midlands.