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Methodology 4.12.b

Cervical Screening Retention Methodology
Short description of Indicator Percentage of Ontario screen-eligible women, 21-66 years old, who had a subsequent Pap test within 42 months of a normal Pap test result
Rationale for measurement Cervical cancer screening using cervical cytology (Pap smear) can lead to early detection of pre-cancerous lesions before they develop into invasive cervical cancer, thereby reducing both cervical cancer incidence and mortality.1

Retention reflects the ability of women to screen repeatedly over time, as well as the acceptability of the screening test.2 Adequate retention in cervical cancer screening is essential for reductions in mortality to occur in the Ontario population.3
Evidence/references for rationale
  1. Andrae B, Kemetli L, Sparen P, Silfverdal L, Strander B, Ryd W, et al. Screening-preventable cervical cancer risks: evidence from a nationwide audit in Sweden. J Natl Cancer Inst. 2008;100(9):622-9.
  2. Canadian Partnership Against Cancer. Cervical cancer screening in Canada: Monitoring program performance 2009–2011. Toronto: Canadian Partnership Against Cancer; 2013.
  3. International Agency for Research on Cancer Prevention; World Health Organization. Handbook of cancer screening volume seven: cervix cancer screening. Lyon: IARCPress; 2005.
Calculations for the indicator [(Total number of Ontario screen-eligible women, 21-66 years old, who had a subsequent Pap test within 42 months of a previous normal Pap test result)/ (Total number of Ontario screen-eligible women, 21-66 years old, who had a normal Pap test in a given year)] x100 =Retention
Standardized Rate Calculation N/A
Unit Percentage (%)
Data sources
  • ​​CytoBase - Pap tests
  • OHIP CHDB (Claims History Database) – Hysterectomy claims
  • OCR (Ontario Cancer Registry) - Resolved invasive cervical cancers
  • RPDB (Registered Persons Database) - Demographics
  • PCCF+, version 6D - Residence and socio-demographic information
Time Frame 2010-2013
Geographic Scale
  • ​Provincial (Ontario)
  • LHIN of residence
  • Public Health Unit (PHU)
Denominator description Total number of Ontario screen-eligible women, 21-66 years old, who had a normal Pap test in a given year
  • Ontario screen-eligible women 21-66 years old at the index date, who had a normal Pap test result in a given year
  • Index date was defined as the last normal Pap test date per person by date of specimen collection in CytoBase in a given year
  • The RPDB address closest to the index date was used to assign postal code
  • Normal Pap tests were defined through CytoBase as NILM (CytoBase codes 4.1, 4.2, 4.3.1, 4.3.2, 4.3 for version 2, and CytoBase codes 4.1, 4.2, 4.3 for version 1)
  • Each woman was counted once in a given year regardless of the number of Pap tests performed
  • LHIN assignment was determined using PCCF+, version 6D; residential postal code was used to identify LHIN
  • Public Health Unit data was determined using PCCF+, version 6D; residential postal code was used to identify public health unit

Exclusions:

  • Women with a missing or invalid HIN, date of birth, LHIN or postal code
  • Women who died during the follow-up period
  • Women diagnosed with an invasive cervical cancer before the subsequent Pap date or during the follow-up interval if there was no subsequent Pap test.
  • Diagnosis of cervical cancer was defined as: ICD-O-3 codes C53, a morphology indicative of cervical cancer, microscopically confirmed with a path report
  • Women with a hysterectomy before the subsequent Pap date or during the follow-up interval if there was no subsequent Pap test
  • Women with a hysterectomy were identified through CHDB, using the following fee codes:
    • E862A – When hysterectomy is performed laparoscopically, or with laparoscopic assistance
    • P042A – Obstetrics – labour – delivery – caesarean section including hysterectomy
    • Q140A – Exclusion code for enrolled female patients aged 35-70 with hysterectomy
    • S710A – Hysterectomy - with or without adnexa (unless otherwise specified) – with omentectomy for malignancy
    • S727A – Ovarian debulking for stage 2C, 3B or 4 ovarian cancer and may include hysterectomy
    • S757A – Hysterectomy – with or without adnexa (unless otherwise specified) – abdominal – total or subtotal
    • S758A – Hysterectomy - with or without adnexa (unless otherwise specified) – with anterior and posterior vaginal repair and including enterocoele and/or vault prolapse repair when rendered
    • S759A - Hysterectomy - with or without adnexa (unless otherwise specified) – with anterior or posterior vaginal repair and including enterocoele and/or vault prolapse repair when rendered
    • S762A - Hysterectomy - with or without adnexa (unless otherwise specified) – radical trachelectomy - excluding node dissection
    • S763A - Hysterectomy - with or without adnexa (unless otherwise specified) – radical (Wertheim or Schauta) - includes node dissection
    • S765A – Amputation of cervix
    • S766A- Cervix uteri - exc - cervical stump – abdominal
    • S767A- Cervix uteri - exc - cervical stump – vaginal
    • S816A - Hysterectomy - with or without adnexa (unless otherwise specified) - vaginal
Numerator description Total number of Ontario screen-eligible women, 21-66 years old, who had a subsequent Pap test within 42 months of a previous normal Pap test result
  • Subsequent Pap tests were identified through CytoBase
  • All tests were considered, regardless of test result
Considerations  N/A
Data availability & limitations
  • ​Only CytoBase data were used for these analyses as there were no results for OHIP data
  • CytoBase includes only Pap tests analyzed in community-based laboratories in Ontario; Pap tests analyzed in Ontario hospitals and Community Health Centres are not captured in CytoBase
  • It is difficult to determine whether a Pap test was done for screening or diagnostic purposes, and therefore, some Pap tests included in these analyses may have been performed for diagnostic purposes
  • Some women with a scheduled Pap test (follow-up) may be included in this cohort
CSQI Year 2018