Performance indicators for participation in organized mammography screening.

Background: A populations acceptance of a screening programme is reflected by its participation. Participation can be measured by cross-section, in an individual screening round, or by cumulative examination rate, which covers participation in numerous rounds at a pre-specified frequency. To establish an informed overview of programme performance, the relationship between these measures was analysed. Methods: The Central Population Register (CPR) of Denmark was used to define the total population. The data sources were mammography screening programmes in Copenhagen (1991-2008) and Funen (1993-2008) and participation and coverage rates were calculated according to European guidelines. Long-term adherence was defined as the cumulative examination rate. Results: The participation rates were 71% in Copenhagen and 91% in Funen. The cumulative examination rates across all invitation rounds were between 21 and 24% lower than the average participation rates. Conclusions: If the cumulative examination rate across all, or the majority of, invitation rounds is substantially lower than the average participation rate it may suggest that standard cross-sectional performance indicators overestimate the level of protection provided to the women targeted by the programme. Consequently, it may prove valuable to include cumulative examination rate as a performance indicator of mammography screening.