National Bowel Cancer Screening Program monitoring report 2026

Determining participation rates by Indigenous status, preferred language spoken at home, and disability status requires the number of screening invitations sent out to members of each of these population groups (the denominator) as well as the number of people in each group who returned a completed screening kit (the numerator).

Unfortunately, at present, information on these groups is known only for participants who choose to identify when they return a completed details form along with their iFOBT for analysis (the numerator). That is, identification of these population groups is known only for the 40% of people who participated, not for all invitees. As a result, it is not possible to accurately determine participation rates for these population groups.

An alternative method to estimate the number of invitations sent out to people in these population groups involves using the percentages of those aged 50–74 who reported as such in the 2021 Census.

To do so, percentages based on Census counts (tables C1–C3) have been applied to the number of overall invitations (by age group and sex) to estimate invitation volumes by population groups. These estimated denominator data can then be used with the known population group numerator data gained from the returned participant details forms of those who participated.

Estimated participation by Indigenous status

There are limitations in the data available to estimate Indigenous Australians’ participation in the NBCSP, due to differences in the ‘not stated’ proportions between the 2021–2022 NBCSP participation data and the 2021 Census data (3.8% and 4.5% ‘not stated’, respectively). An overall participation rate for invitees who self-identified as Indigenous has been estimated (see Equity in the NBCSP), but these limitations should be considered when interpreting these data.

Opportunities to improve the accuracy of calculating Indigenous Australian participation rates will continue to be explored. New information may become available that enables improved estimates to be produced for future reports.

Source: 2021 Census.

Estimated participation by language spoken at home

Census data for population subgroups broken down by the language they spoke at home include a ‘not stated’ percentage for those who did not respond to this question (Table C2). This is equal to the ‘not stated’ option for those who participate and choose not to provide population group information.

For preferred language spoken at home, the NCSR assumes all who do not self-identify a language speak English. As a result, there is no ‘not stated’ language spoken at home data for participants (numerator) to match the ‘not stated’ percentage data from the Census (used for the denominator).

To resolve this issue, a participation range method was used for language spoken at home. The rate is provided as a range that covers what the percentage would be if the entire ‘not stated’ percentage was added to the ‘English’ column, and what it would be if the entire ‘not stated’ percentage was added to the ‘Language other than English’ column (Table 4.4).

Source: 2021 Census.

Estimated participation by disability status

Census data for population subgroups broken down by disability status include a ‘not stated’ percentage for those who did not respond to this question (Table C3). This should equate to the ‘not stated’ option for those who participate and choose not to provide population group information.

However, due to changes in completeness of disability status information in the NCSR, estimates of participation rates by disability status could not be reported in the current report (Table 4.5).

Source: 2021 Census.