Performance indicators for participation in organized mammography screening

A population's 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.

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.

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.

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.