Technical notes

Age-specific rates

The number of cases occurring in each specified age group divided by the corresponding population in the same age group. For example, in this report age-specific participation rates are calculated as the number of people participating in a screening program, divided by the number of people eligible to participate (or the number of people in the population of that age), expressed as a percentage.

Age-standardised rates

Age-standardisation is a way to remove the influence of age when comparing populations with different age structures (or relative number of people in each age group in a population). This is usually necessary because the rates of many diseases vary strongly (usually increasing) with age. The age structures of the different populations are converted to the same ‘standard’ structure, and then the disease rates that would have occurred with that structure are calculated and compared.

In this report the presentation of participation rates by state or territory and age group shows age-standardised rates for the target age group for BreastScreen Australia (50–69 and 50–74) and the National Cervical Screening Program (20–69). All other rates within this report are age-specific (crude) rates.

Geography

Participation rates in the NBCSP, BreastScreen Australia and the NCSP are presented for the following geographies:

  • Primary Health Network (PHN) areas: 31 areas covering Australia, defined by the Department of Health (Department of Health 2018).
  • Statistical Areas Level 3 (SA3s): 333 areas covering Australia.

Participation rates in the NBCSP are also presented for:

  • Statistical Areas Level 2 (SA2s): 2,196 areas covering Australia.

Both SA3s and SA2 are defined by the ABS within the Australian Statistical Geography Standard:

  • The 2011 ASGS was used for the NBCSP, the NCSP, and 2014–2015 and 2015–2016 BreastScreen Australia data in this report.
  • The 2016 ASGS was used for the 2016–2017 BreastScreen Australia data in this report.

Assigning geography

For NBCSP invitees, geographic areas (PHN areas, SA3s and SA2s) were assigned using Statistical Area Level 1 (SA1) of usual residence. For invitees without reliable SA1 details geographic areas were assigned using postcode of usual residence. As some postcodes cross the boundaries of PHNs, SA3s or SA2s the use of postcode correspondences may lead to some minor inaccuracies in results.

Where SA1 codes and postcodes could not be attributed to a PHN, SA3 or SA2, these invitees were included in an 'Unknown' group in the data tables, and are excluded from data visualisations.

For BreastScreen Australia and NCSP data, PHN areas and SA3s were assigned using postcode of usual residence. Where postcodes could not be attributed to a PHN or SA3, these women were included in an ‘Unknown’ group, where possible in the data tables, and were excluded from data visualisations. Note that NCSP postcodes are used for mailing purposes and may not reflect where a woman resides.

For analyses for all three cancer screening programs, where a postcode or SA1 boundary overlapped PHN areas, SA3 or SA2 boundaries, the relevant records were attributed based on the percentage of the population within that postcode or SA1 that fell within the PHN area SA3, or SA2.

Correspondences

Correspondence files for PHN were sourced from the Australian Statistical Geography Standard (ASGS): Volume 3 — Non ABS Structures (ABS 2011, 2016).  For the NBCSP, the NCSP data, and BreastScreen Australia data for 2014–2015 and 2015–2016, data were classified according to the PHN 2015 structure (ABS 2011). BreastScreen Australia 2016–2017 data were classified according to the PHN 2017 structure (ABS 2016). PHNs were established in June 2015, and some of the geographic information presented includes data before that date. For further details on PHNs see the Department of Health’s website.

For the NBCSP, the NCSP data, and BreastScreen Australia data for 2014–2015 and 2015–2016, correspondence files for SA3s and SA2s were sourced from Australian Statistical Geography Standard (ASGS) 2011: Volume 1 (ABS 2010). For 2016–2017 BreastScreen Australia data correspondence files for SA3s were sourced from Australian Statistical Geography Standard (ASGS) 2016: Volume 1 (ABS 2016).

The correspondences produced by the ABS can be found on data.gov.au  by searching for: ‘ASGS’, the ‘year’, and ‘correspondences’.

The number of people in different geographic areas (PHNs, SA3s or SA2s) may not sum to ‘Australia’ total due to rounding. The Australia total also includes some records that could not be attributed to a geographic area.

SA3s and SA2s with a numerator less than 20 or a denominator less than 100 were suppressed.

For a full list of AIHW products that include data and results by small areas (for example, by Primary Health Network areas) see AIHW data by geography.

Participation rates

NBCSP

Two-yearly screening for those aged 50–74 has not been fully rolled out. During the time period reported (up to 2016–2017) the ages invited to participate were 50, 54, 55, 58, 60, 64, 65, 68, 70, 72 and 74. Participation rates represent the percentage of people invited to screen through the NBCSP during the relevant 2-year period, who returned a completed screening test within that period or by 30 June of the following year. The number of individuals invited to screen excludes those who deferred or opted out without completing their screening test.

NBCSP data in this report covers the period 1 January 2014 to 31 December 2017.

BreastScreen Australia

Participation rates represent the percentage of women in the population aged 50­–74 screened by BreastScreen Australia over 2 calendar years. The population denominator was the average of ABS Estimated Resident Population (ERP) for females aged 50–74 within the relevant geographical area (PHN, SA3) for the relevant 2-year reporting period.

BreastScreen Australia changed its target age group from 50–69 years to 50–74 years from July 2013; participation is reported for both the previous and current target age groups to allow comparison of trends with previously reported data. BreastScreen Australia data in this report covers the period 1 January 2014 to 31 December 2017.

NCSP

Participation in the NCSP for this report was defined as the percentage of women in the population aged 20–69 who had at least one Pap test in a 2-year period. Participation rates were calculated using the average of ABS Estimated Resident Population (ERP) for females aged 20–69 for the relevant 2-year reporting period adjusted for the estimated proportion of women who have had a hysterectomy.

Some duplication may occur where the same test is reported to the cervical screening register in two or more jurisdictions. This may lead to erroneous results when focusing on smaller geographical areas. This may affect border areas more than other areas. Participation rates were suppressed in cases where this may have substantially affected data quality.

While the new NCSP began in December 2017 for women aged 25–74, data in this report are for women screened under the previous program, so use the target age group of 20–69 appropriate to that program. NCSP data in this report cover the period 1 January 2014 to 31 December 2016.

State or territory

For the NBCSP, state or territory reported refers to the state or territory of residence. For BreastScreen Australia and the NCSP, state or territory reported refers to the state or territory in which screening occurred, not the state or territory of residence.

Data sources

AIHW analysis of National Bowel Cancer Screening Program register data, state and territory BreastScreen Australia register data and state and territory cervical screening register data.

References

Australian Bureau of Statistics (ABS) 2010. Australian Statistical Geography Standard (ASGS): Volume 1 — Main Structure and Greater Capital City Statistical Areas, July 2011. ABS cat. no. 1270.0.55.001. Canberra: ABS.

ABS 2010. Australian Statistical Geography Standard (ASGS): Volume 3 — Non ABS Structures, July 2016. ABS cat. no. 1270.0.55.003. Canberra: ABS.

ABS 2016. Australian Statistical Geography Standard (ASGS): Volume 1 — Main Structure and Greater Capital City Statistical Areas, July 2016. ABS cat. no. 1270.0.55.001. Canberra: ABS.

ABS 2016. Australian Statistical Geography Standard (ASGS): Volume 3 — Non ABS Structures, July 2016. ABS cat. no. 1270.0.55.003. Canberra: ABS.

Department of Health 2018. Primary Health Networks (PHNs). Canberra: Department of Health. Viewed 17 December 2018.