Breast Screening - Ontario Breast Screening Program (OBSP)

 

Regional variation in OBSP coverage, by LHIN, women aged 50-69, 2007 and 2008-2009

Coverage
Target Waterloo Wellington 95% CI OBSP 95% CI
Women screened (n)
  35,368   636,511  
Participation rate (%)
≥ 70% 44.9 44.4-45.3 42.0 41.9-42.1
Retention rate* (%)
initial screens ≥ 75% 79.8 78.8-80.9 77.3 77.1-77.6
rescreens ≥ 90% 89.9 89.3-90.5 88.3 88.2-88.5
Participation Rate - The percentage of screen-eligible Ontario women (50-69 years old) who have completed at least one screen in the OBSP in a two-year time period.
Retention Rate - The percentage of screen-eligible women who were rescreened within 30 months of their previous program screen for initial and subsequent screens.
Data Source: Integrated Client Management System, 2010
* Retention rate for women screened in 2007

Regional variation in OBSP follow-up, by LHIN, women aged 50-69, 2008

Follow-Up
Target Waterloo Wellington 95% CI OBSP 95% CI
All screens (n)
initial screens   6,838   101,785  
rescreens   11,324   260,783  
Abnormal screens (n)
initial screens   511   12,769  
rescreens   463   18,130  
Abnormal call rate (%)
initial screens < 10% 7.5 6.8-8.1 12.5 12.3-12.8
rescreens < 5% 4.1 3.7-4.5 7.0 6.9-7.1
Diagnostic interval (%) (%)
within 5 weeks without a tissue biopsy
≥ 90% 82.3 76.1-88.8 81.1 80.0-82.2
within 7 weeks with a tissue biopsy
≥ 90% 53.0 42.5-65.2 55.7 53.5-58.0
Abnormal Call Rate - The percentage of screens that are referred for further testing because of an abnormal result for initial and subsequent screens.
Diagnostic interval (%) - Duration (in weeks) from abnormal screen to diagnosis (benign or cancer) for initial and subsequent program screens combined.
Data Source: Integrated Client Management System, 2010

 

Regional variation in OBSP quality of screening, by LHIN, women aged 50-69, 2007 and 2008

Quality of Screening
Target Waterloo Wellington 95% CI OBSP 95% CI
Abnormal screens (n)
initial screens   507   12,484  
rescreens   461   17,860  
Breast cancers (n)
initial screens   40   580  
rescreens   46   1,098  
Positive predictive value* (%)
initial screens ≥ 5% 7.9 5.6-10.7 4.6 4.3-5.0
rescreens ≥ 6% 10.0 7.3-13.3 6.1 5.8-6.5
One-year sensitivity** (%)
  79.1 59.3-100 88.1 83.8-92.6
One-year specificity** (%)
  95.1 93.5-96.7 92.2 91.9-92.6
Positive Predictive Value - The percentage of abnormal cases with completed follow-up found to have breast cancer (ductal carcinoma in situ [DCIS] or invasive) after diagnostic work-up for initial and subsequent program screens.
Sensitivity -The proportion of women diagnosed with a screen-detected DCIS and/or invasive breast cancer following completion of diagnostic assessment who had a positive screening test for breast cancer (for initial and subsequent program screens combined).
Specificity - The proportion of women without a diagnosis of DCIS and/or invasive breast cancer who had a negative screening test for breast cancer (for initial and subsequent program screens combined).
Data Source: Integrated Client Management System, 2010
Upper confidence limit was set to a maximum of 100
* Positive predictive values for women screened in 2008      ** Sensitivity and Specificity for women screened in 2007

Regional variation in OBSP detection, by LHIN, women aged 50-69, 2008

Detection
Target Waterloo Wellington 95% CI OBSP 95% CI
All screens minus those screens with final results unknown (n)
initial screens   6,834   101,500  
rescreens   11,322   260,513  
Breast cancers (n)
in situ initial   4   92  
in situ rescreens   6   182  
invasive initial   36   488  
invasive rescreens   40   916  
In situ cancer detection rate (per 1,000 screens)
initial screens   0.6 0.2-1.5 0.9 0.7-1.1
rescreens   0.5 0.2-1.2 0.7 0.6-0.8
Invasive breast cancer detection rate (per 1,000 screens)
initial screens > 5  5.3 3.7-7.3 4.8 4.4-5.3
rescreens > 3 3.5 2.5-4.8 3.5 3.3-3.8
In Situ Breast Cancer Detection Rate - The number of women detected with DCIS breast cancer during a screening episode per 1,000 women screened for initial and subsequent program screens.
Invasive Breast Cancer Detection Rate - The number of women detected with invasive breast cancer during a screening episode per 1,000 women screened for initial and subsequent program screens.
Data Source: Integrated Client Management System, 2010

Regional variation in OBSP disease extent at diagnosis, by LHIN, women aged 50-69, 2008

Disease Extent at Diagnosis
Waterloo Wellington 95% CI OBSP 95% CI
Invasive breast cancers with known TNM stage group (n)
73.0   1,218  
Stage I invasive breast cancer (%)
61.6 45.0-82.5 62.2 57.9-66.8
Early Stage Invasive Breast Cancer Detection Rate - The percentage of invasive screen-detected breast cancers detected at an early stage (TNM stage I) for initial and subsequent program screens combined.
Data Source: Integrated Client Management System, 2010