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Breast Cancer Screening Quality Methodology

Breast Cancer Screening (Mammogram) Positive Predictive Value (PPV)
Short description of Indicator Percentage of Ontario screen-eligible women with an abnormal OBSP screening mammogram result, 50-74 years old, who were diagnosed with breast cancer (DCIS or invasive) after diagnostic work-up
Rationale for measurement The Canadian Partnership Against Cancer recommends a suite of breast cancer screening program evaluation indicators to provide consistent calculation of key indicators for monitoring and evaluation efforts across programs and over time.[1] Positive Predictive Value is a performance indicator that is recommended for measurement by CPAC in their 2013 guidelines for monitoring breast cancer screening program performance.[1] Positive predictive value is a quality measure that assesses the accuracy of breast cancer screening in women with breast cancer.[1] [2] [3] A high positive predictive value indicates a minimization of unnecessary follow-up procedures.[2] The Canadian target for positive predictive value is ≥5% for initial screens and ≥6% for re-screens.[1] [2] [3]
Evidence/references for rationale
  1. Canadian Partnership Against Cancer. Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Cancer Screening Program Performance (3rd Edition). Toronto: Canadian Partnership Against Cancer; February, 2013.
  2. Canadian Partnership Against Cancer. Breast Cancer Screening in Canada: Monitoring and Evaluation of Quality Indicators- Results Report, December 2009–January 2010. Toronto (ON): Canadian Partnership Against Cancer; 2015.
  3. Cancer Care Ontario. Ontario Breast Screening Program 2011 report. Toronto, Ontario: Cancer Care Ontario; 2013.
Calculations for the indicator (Total number of Ontario screen-eligible women, 50-74 years old, who had an abnormal OBSP screening mammogram result, who were diagnosed with a screen-detected breast cancer (DCIS or invasive) after diagnostic work-up / Total number of Ontario screen-eligible women, 50-74 years old, who had an abnormal OBSP screening mammogram) X 100
Standardized Rate Calculation N/A
Unit Percentage (%)
Data sources
  • ICMS (Integrated Client Management System) - OBSP mammograms
  • OHIP CHDB (Claims History Database) - Mastectomy claims
  • OCR (Ontario Cancer Registry) - Invasive and in-situ breast cancers
  • RPDB (Registered Persons Database) – Demographics
  • PCCF+ - Residence and socio-demographic information
Time Frame 2014 - 2017
Geographic Scale Provincial (Ontario)
Denominator description Total number of Ontario screen-eligible women, 50 to 74 years old, who had an abnormal OBSP screening mammogram result
  • Average risk women, ages 50 to 74 at the index date, who had an abnormal OBSP screening mammogram result
  • Index date was defined as the first OBSP screening mammogram date per woman in the Integrated Client Management System (ICMS) in a given year
  • Each woman was counted once regardless of the number of screening mammograms performed
  • An abnormal screening mammogram result was defined as an OBSP screening mammogram referred for further testing by the screening radiologist in the ICMS

Exclusions:

  • Women with a missing or invalid HIN, date of birth, postal code or LHIN
  • Women with a prior diagnosis of invasive or in-situ breast cancer before the index date; prior diagnosis of breast cancer was defined as: ICD-O-3 codes: C50, a morphology indicative of ductal carcinoma in-situ or invasive breast cancer, microscopically confirmed with a path report
  • Women with a mastectomy before the index date; mastectomy was defined in OHIP by fee codes E546, R108, R109, E505, E506 and R117
  • Women lost to follow-up or final diagnosis is unknown
Numerator description Total number of Ontario screen-eligible women, 50 to 74 years old, who had an abnormal OBSP screening mammogram result, who were diagnosed with a screen-detected breast cancer (DCIS or invasive) after diagnostic work-up
Considerations  This indicator does not include OHIP billings for women screened outside of the OBSP since the OHIP database does not contain information about the results of the screening test or the results of the follow-up diagnostic work-up and final definitive diagnosis
Data availability & limitations
  • This indicator includes OBSP mammograms only
  • There is at least an 8-month reporting lag for this indicator as the regions have up to and including 8 months to close off assessment cases and enter the information to the Integrated Client Management System (ICMS)
CSQI Year 2019