Cervical Screening Participation in Victoria (2016-2020, 2017-2021, 2018-2022)
1. Definition
- Cervical cancer screening five-year participation in calendar years is calculated using:
- Numerator: Number of participants aged 25-74 who had at least one HPV test or cytology test for any reason in Victoria in the five-year reporting periods. The five-year reporting periods are based on the calendar years (e.g., 01/01/2018 - 31/12/2022)
- Denominator: Average of Australian Bureau of Statistics (ABS) estimated resident population (ERP) over the five-year reporting periods, adjusted for Hysterectomy fractions and current Compass trial participants in Victoria.
- Currently national reporting of participation rates does not adjust for Compass trial participants (compasstrial.org.au).
2. Data source: NCSR Raw Data Extract (RDE) Sep 2022
- 01 Jan 2016 - 31 Dec 2020 (five years participation)
- 01 Jan 2017 - 31 Dec 2021 (five years participation)
- 01 Jan 2018 - 31 Dec 2022 (five years participation)
3. Count is of women, not Cervical Screening Tests (CSTs).
4. The table provides the percentage of women screened as a proportion of the eligible female population (crude rate).
5. Methodology for calculating participation:
- Join the HPV Cytology Data Items and Person tables from the Raw Data Extract (RDE) using Registry Reference Number (RRN) as a key.
- Filter tests on date of procedure for the periods needed i.e., 01 Jan 2016 - 31 Dec 2020, 01 Jan 2017 - 31 Dec 2021, and 01 Jan 2018 - 31 Dec 2022
- Calculate age at the time of the episode using a function in MS Excel called DATEDIF that calculated the difference in years between the date of birth and the date of procedure.
- Filter tests of participants with an age at test between the ages of 25-74
- Select eligible tests (HPV, HPV + LBC, LBC):
HPV test collection method = 2 Self-collection were included
HPV test collection method = 1 Practitioner-collected sample and the HPV test specimen site equal to B1-Cervical or B0-Not stated were included
CSTs with a cytology endocervical (glandular) cytology cell analysis = E- Not applicable: vault smear/previous hysterectomy were excluded
- Sort eligible tests by Date of procedure (oldest to newest)
- For each period, select one test per client - the first test of the period (i.e., remove duplicates by RRN).
- Allocate a postcode at the time of the episode. Join dataset with RDE Address Fix table using HPV Cytology ID as a key.
- Reallocate some postcodes based on the address details (for instance PO boxes were allocated to the suburb of the address).
- Eligible population: ABS 2022, customised report. ERP by Single year of age by sex by Postal Areas, Australia, Reference Period: 30 June for each year. Final versions of ERP were used to calculate the denominator for 2016 - 2021 data, while a preliminary version was used for the 2022 data.
- Hysterectomy fractions for the new cervical screening program (i.e., with women aged 70-74 years included) were applied to the ERP. Sourced from the ABS in Feb 2019, not for publication. https://www.aihw.gov.au/getmedia/fcacac12-cd05-4325-88bc-5529a61b53f3/aihw-can-132.pdf?v=20230605165635&inline=true
- All Women that participated in the Compass trial* are not included in the NCSR RDE (women screened), therefore these Compass women were deducted from the eligible population (i.e. Compass women who had a Compass episode were deducted from the ERP that had Hysterectomy fractions applied).
- For women that have exited the Compass trial, they were removed from the Compass list and counted in the eligible population for cervical screening.
6. The mapping of the data for Local Government Areas (LGAs) is based on concordances consistent with the ABS Australian Statistical Geography Standard (ASGS).
- Participation data by Local Public Health Unit (LPHU) are calculated as an aggregate of LGAs as per LGA to LPHU concordance table provided by the Department of Health in Sep 2022.
7. Geocoding of address to determine geographic breakdowns will be used for future data when available. Correspondences were used for this data.
8. To convert data from postcode to LGA we used the following concordances:
- ASGS Geographic Correspondences Table 3 of file named CG_POSTCODE_2022_LGA_2022, which is a 2016 Mesh Block population weighted correspondence file.
- Source: www.data.gov.au
- Search for: ABS ASGS Correspondences
- Click on: ASGS Geographic Correspondences (2021)
- Download: ASGS Edition 3 (2021) Correspondence Files (ZIP)
- File name: CG_POSTCODE_2022_LGA_2022
- Postcodes not listed in concordances were mapped manually.
- Participants with Victorian postcodes mapped to LGAs outside Victoria were excluded from LGA and Health Region tables and therefore overall totals may not align with state totals.
9. To convert data from postcode to Primary Health Network (PHN) we used the following concordances:
- ASGS Geographic Correspondences Table 3 of file named CG_POSTCODE_2021_PHN_2017, which is a 2016 Mesh Block population weighted correspondence file.
- Source: www.data.gov.au
- Search for: ABS ASGS Correspondences
- Click on: ASGS Geographic Correspondences (2021) Edition 3
- Download: ASGS Edition 3 (2021) Correspondence Files (ZIP)
- File name: CG_POSTCODE_2021_PHN_2017
- Postcodes not listed in concordances were mapped manually.
- Participants with Victorian postcodes mapped to PHNs outside Victoria were excluded from PHN tables and therefore overall totals may not align with state totals.
10. Participation rates for some LGAs by five-year age group was over 100%. There are different reasons why something like this could occur, for example seasonal populations such as holiday locations can cause the number of women screened to become higher than the resident population.
- Areas with smaller populations are also subject to greater error and variability, as sometimes a little change can have a significant percentage difference.
- Also, to convert postcode data to LGA we use the ASGS Correspondences. Some postcodes are split up over two or more LGAs.
- These correspondences include a ratio figure between 0 and 1. When applying ratios to the number of women, it is therefore possible to get less than one woman (decimal points).
- Considering the factors mentioned above and to avoid confusion, for women screened less than zero, eligible population equal to zero, and rates over 100%, the screening rate was omitted and marked with an asterisk (*) in the tables.
11. Please note that the pandemic impacted screening services and health seeking behaviours which will be reflected in the 2020-2022 data.
