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4B Screening Mammography

Description |  Specific Indicators |  Ontario Public Health Standards (OPHS) Corresponding Indicators from Other Sources |  Data Sources |  Survey Questions |  Alternative Data Sources | Analysis Check List |  Method of Calculation |  Basic Categories |  Indicator Comments  | Cross-References to Other Indicators |  Cited References | Changes Made


  • Proportion of women aged 50-69 reporting having a screening mammogram in the past two years.

Specific Indicators

  •   Screening mammography rate

Ontario Public Health Standards (OPHS)

The Ontario Public Health Standards (OPHS) establish requirements for the fundamental public health programs and services carried out by boards of health, which include assessment and surveillance, health promotion and policy development, disease and injury prevention, and health protection. The OPHS consist of one Foundational Standard and 13 Program Standards that articulate broad societal goals that result from the activities undertaken by boards of health and many others, including community partners, non-governmental organizations, and governmental bodies. These results have been expressed in terms of two levels of outcomes: societal outcomes and board of health outcomes. Societal outcomes entail changes in health status, organizations, systems, norms, policies, environments, and practices and result from the work of many sectors of society, including boards of health, for the improvement of the overall health of the population. Board of health outcomes are the results of endeavours by boards of health and often focus on changes in awareness, knowledge, attitudes, skills, practices, environments, and policies. Boards of health are accountable for these outcomes. The standards also outline the requirements that boards of health must implement to achieve the stated results.

Outcomes Related to this Indicator

  • Board of Health Outcome (Chronic Disease Prevention): The public is aware of the benefits of screening for early detection of cancers and other chronic diseases of public health importance.

Health Promotion and Policy Development Requirements Related to this Indicator

  • The board of health shall collaborate with community partners to promote provincially approved screening programs related to the early detection of cancers (Chronic Disease Prevention). 
  • The board of health shall increase public awareness in the following areas...benefits of screening for early detection of cancers and other chronic diseases of public health importance...These efforts shall include:

a. Adapting and/or supplementing national and provincial health communications  strategies; and/or 

b. Developing and implementing regional/local communications strategies (Chronic Disease Prevention).

  • The board of health shall provide advice and information to link people to community programs and services on the following topics...Screening for chronic diseases and early detection of cancers (Chronic Disease Prevention).


Corresponding Indicator(s) from Other Sources

Search for "Cancer System Quality Index", then "Access" and then "Breast cancer screening".1

  • Percentage of screen-eligible women (ages 50-69) receiving a mammogram within the past two years, by type of screening (whether through the OBSP or outside the program), in Ontario.

Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Screening Program Performance

Percentage of women who have a screening mammogram (calculated biennially) as a proportion of the eligible population.

Data Sources

Numerator & Denominator: Canadian Community Health Survey (CCHS)
Original source:
Statistics Canada
Distributed by:
1. Ontario MOHLTC
2. Statistics Canada
Suggested citation (see Data Citation Notes):

1. Canadian Community Health Survey [year], Statistics Canada, Share File, Ontario MOHLTC
2. Canadian Community Health Survey [year], Statistics Canada, Public Use Microdata File, Statistics Canada

Survey Questions

Canadian Community Health Survey 2000/01 2003, 2005, 2007 Questions:

There is a Mammography module in the CCHS and this module was core content in 2000-01, 2003 and 2005. This module was optional content and selected by Ontario in 2007. These questions are asked for women who are 35 years of age and over.


Data Source



Response Categories





Have you ever had a mammogram, that is, a breast x-ray?

Don't Know,









Why did you have it?

Family history of breast cancer,
Part of regular check-up / routine screening,
Previously detected lump, Follow-up of breast cancer treatment,
On hormone replacement therapy,
Breast problem,
Other - specify









When was the last time?

Less than 6 months ago,
6 months to less than 1 year ago,
1 year to less than 2 years ago,
2 years to less than 5 years ago,
5 or more years ago









Alternative Data Source(s)

The Rapid Risk Factor Surveillance System (RRFSS) contains a module called Mammography II. This module was optional from 2001-2008.

Data Source



Response Categories




Mammography II

Have you ever had a mammogram, that is, a breast x-ray?

don't know, refused



Did you have your last mammogram within the last two years?

don't know, refused



Can you tell me how many years ago you last had a mammogram?

enter exact number of years,
don't know, refused



For which one of the following three reasons did you have your last mammogram: would you say it was for ONE, a regular check-up or routine visit; TWO, an ongoing or past problem, or THREE, a concern about a possible problem?

regular check-up/routine visit,  ongoing/past problem,  concern about a possible problem



Analysis Check List

  • To identify those who had a mammogram in the last two years in the CCHS, combine response categories 1, 2 and 3 for question MA_Q032/ MAM_Q032.
  • The numerator is defined as women aged 50-69 in CCHS who report having had a mammogram in the previous two years for one or more of the following reasons: family history of breast cancer, part of regular check-up / routine screening, age, on hormone replacement therapy. These respondents must not have had a mammogram in the previous two years because of a previously detected lump, follow-up of breast cancer treatment, breast problem or ‘other' reason.
  • If using RRFSS, the response mam4=1 (regular check-up or routine visit) is the reason for mammogram that is meant to capture screening mammography, and should form the numerator.


  • It is recommended that public health units use the Share File provided by the Ministry of Health and Long-Term Care rather than public use file (PUMF) provided by Statistics Canada. The Share File has a slightly smaller sample size because respondents must agree to share their information with the province to be included; however, the share file has more variables and fewer grouped categories within variables. The Share File is a cleaner dataset for Ontario analysis because all variables that were not common content, theme content or optional content for Ontario have been removed.
  • There may be slight differences between results from the share file and data published on the Statistics Canada website for the Health Indicators because rates calculated for Health Indicators use the master CCHS data file.
  • Not applicable respondents should be excluded; however, it is important to understand who these respondents are from the questionnaire skip patterns to be able to describe the relevant population.
  • Users need to consider whether or not to exclude the ‘Refusal, 'Don't Know' and ‘Not Stated' response categories in the denominator. Rates published in most reports, including Statistics Canada's publication Health Reports generally exclude these response categories. In removing not stated responses from the denominator, the assumption is that the missing values are random, and this is not always the case. This is particularly important when the proportion in these response categories is high.
  • Estimates must be appropriately weighted (generally the share weight for the CCHS) and rounded.
  • Users of the CCHS Ontario Share File must adhere to Statistics Canada's release guidelines for the CCHS data when publishing or releasing data derived from the file in any form. Refer to the appropriate user guide for guidelines for tabulation, analysis and release of data from the CCHS. In general, when calculating the CV from the share file using the bootstrap weights, users should not use or release weighted estimates when the unweighted cell count is below 10. For ratios or proportions, this rule should be applied to the numerator of the ratio.  Statistics Canada uses this approach for the tabular data on their website. When using only the Approximate Sampling Variability (CV) lookup tables for the share file, data may not be released when the unweighted cell count is below 30. This rule should be applied to the numerator for ratios or proportions.  This provides a margin of safety in terms of data quality, given the CV being utilized is only approximate.
  • Before releasing and/or publishing data, users should determine the CV of the rounded weighted estimate and follow the guidelines below:
    • Acceptable (CV of 0.0 - 16.5%) Estimates can be considered for general unrestricted release. Requires no special notation.
    • Marginal (CV of 16.6 - 33.3%) Estimates can be considered for general unrestricted release but should be accompanied by a warning cautioning subsequent users of the high sampling variability associated with the estimates. Such estimates should be identified by the letter E (or in some other similar fashion).
    • Unacceptable (CV greater than 33.3%) Statistics Canada recommends not to release estimates of unacceptable quality. However, if the user chooses to do so then estimates should be flagged with the letter F (or in some other fashion) and the following warning should accompany the estimates: "The user is advised that...(specify the data) not meet Statistics Canada's quality standards for this statistical program. Conclusions based on these data will be unreliable and most likely invalid". These data and any consequent findings should not be published. If the user chooses to publish these data or findings, then this disclaimer must be published with the data.
  • Caution should be taken when comparing the results from Cycle 1.1 (2000/01) to subsequent years of the survey, due to a change in the mode of data collection.  The sample in Cycle 1.1 had a higher proportion of respondents interviewed in person, which affected the comparability of some key health indicators.  Please refer to for a full text copy of the Statistics Canada article entitled "Mode effects in the Canadian Community Health Survey: a Comparison of CAPI and CATI".


  • Users should refer to the most recent RRFSS Manual of Operations for a complete list of RRFSS analysis guidelines.
  • Denominator Data - cell size less than 30 not to be released (based on unweighted data).
  • Numerator Data - cell size less than 5 not to be released (based on unweighted data).
  • Coefficients of variation (CV) should be calculated for every estimate. The following categories determine the release of the data:
    • CV between 0 and 16.5: estimate can be released without qualification.
    • CV between 16.6 and 33.3: estimate can be released with qualification: interpret with caution. High variability.
    • CV greater than 33.3:  estimate should not be released, regardless of the cell size.
  • 95% confidence intervals should accompany all released estimates. In general the simple computation of the C.I. for a proportion assuming SEp = sqrt(pq/n) and CI95% = p +/- 1.96*SEp is sufficient. However, if estimates are close to 0 or 100% and the simple computation confidence intervals include values less than zero or greater than 100 then the Fleiss 2nd edition computation for skewed estimates should be employed.
  • Weighting:
    • General household weight will be applied for questions related to the individual. 
    • Household weight is to be applied for questions about households when we wish to determine the population/number of people affected. 
    • Household weight is not to be applied for child proxy questions (bicycle helmet use, car seat safety), dog and cat immunization modules, or other questions that relate to the household rather than the respondent. 
    • Household weights are not required to be recalculated for sub-population based questions; for example mammography in women ages 35+ years and 50-74 years.
    • If the weights supplied with the data set (health unit wave specific, health unit cumulative total, all health units combined wave specific, all health units combined cumulative total) are not appropriate for the required analysis, then a time-specific weight must be calculated.  For example, a new weight is required for all seasonal modules.
  • If the cell size of ‘Don't Know' responses is 5% or greater, ‘Don't Know' responses should be included in the denominator of the analyses and reported separately.
  • If the cell size of ‘Refusal' responses is 5% or greater, ‘Refusal' responses should be included in the denominator of the analyses and reported separately.
  • When an indicator is being compared between groups (e.g. health units, time periods, gender), if any one group has ‘Don't Know' and/or ‘Refusal' responses that are 5% or greater, ‘Don't Know' and/or ‘Refusal' responses should be included in the denominator of the analyses and reported separately for all groups.
  • A provincial sample is not available with the RRFSS.
  • Refer to the RRFSS Data Dictionaries at for more information about module questions and indicators. 


Method of Calculation

Number of women aged 50-69 reporting having a screening mammogram in past two years
Total number of women aged 50-69
 X 100

Numerator is defined as women aged 50-69 in CCHS who report having had a mammogram in the previous two years for one or more of the following reasons:

1 Family history of breast cancer
2 Part of regular check-up / routine screening
3 Age
6 On hormone replacement therapy

and not for any of the following reasons

4 Previously detected lump
5 Follow-up of breast cancer treatment
7 Breast problem
8 Other - Specify


Basic Categories

  •  Geographic areas for CCHS: Public Health Unit and LHIN; RRFSS- all participating health units.


Indicator Comments

  • Screening is checking for a disease or condition when there are no symptoms. Diagnosis is identifying a disease or condition from its signs and symptoms. Some cancer detection tests may be performed for either screening or diagnostic reasons.Breast screening using mammography is recommended for women aged 50 through 69 by the International Agency for Research on Cancer of the World Health Organization, the U.S. Preventive Services Task Force and the Canadian Task Force on Preventive Health Care.
  • The specification of the numerator in "Method of calculation", above, assumes that, when both screening and diagnostic reasons for mammography are reported, the reason is diagnostic. It is, however, possible that a woman had first a screening and then a diagnostic mammogram within the previous two years and is reporting both of those. Evaluation of Ontario data for CCHS 2.1 (2003) suggests that if the numerator were specified to include women who reporting both screening and diagnostic reasons for mammography, the estimate would be increased from 61% to 64%. Cancer Care Ontario's recommendation is to use the more conservative method (numerator consisting of women who reported only screening reasons), since self-report is usually considered an overestimate. (Loraine Marrett, Michael Spinks, Beth Theis, Cancer Care Ontario, 2006).
  • Women who report having had breast cancer have not been removed from the numerator or denominator, although CCHS data would allow for this. Cancer Care Ontario's recommendation is to leave them in: numbers are probably small, OBSP does not routinely do this, there is no standard agreement on whether, and when, women with a history of breast cancer should revert to the population screening recommendation, and without sequence information in CCHS data it is possible that a woman reporting a history of breast cancer was diagnosed as a result of breast screening. (Verna Mai, Anna Chiarelli, Beth Theis, Cancer Care Ontario, 2006).
  • This indicator, unlike the Cancer System Quality Index indicator, does not specify that it is measuring "screen-eligible" women. This is partly because women who have had breast cancer are not removed from the denominator in the Method of Calculation, and partly because definitions of "Screen-eligible" are subject to change over time, with changing recommendations.
  • "Screening Mammography", as an indicator additional to an "Ontario Breast Screening (OBSP) Mammography" indicator, recognizes that a considerable proportion of Ontario women have screening mammography outside the Ontario Breast Screening Program. This indicator captures women who self-report screening mammography and includes those screened within the Ontario Breast Screening Program and outside the organized provincial program. Ontario's Cancer System Quality Index typically publishes a comparison of the proportion of Ontario women screened within and outside the OBSP; for 2005-2006, an estimated 54% of mammographic screening of Ontario women aged 50-69 occurred within the OBSP.1
  • While breast screening by any provider may be effective, that offered within an organized program has important quality advantages, accessibility and reminders, and uses a set of nationally derived program performance measures.2,3
  • The data used for this indicator are self-reported. The rate of mammographic screening may therefore be over or under-estimated. Self-report data may be subject to errors in recall, over or under-reporting due to social desirability, and errors from proxy reporting. Despite these potential shortcomings, an estimate of 58.5% of Ontario women screened in 2002-2003 prepared from the Ontario Health Insurance Plan and Registered Persons databases for the Cancer System Quality Index was close to estimates of 61% from the CCHS 2003 using the method of calculation described above, which is used by staff at both Cancer Care Ontario and the Public Health Agency of Canada.1,4















Cross-References to Other Indicators

 Cited Reference(s)

  1. Cancer Care Ontario: Cancer System Quality Index: Breast cancer screening (mammography) participation, 2008. Available online: (Accessed February 10, 2009).
  2. Cancer Care Ontario. Insight on Cancer- News and information on breast cancer and screening in Ontario. Toronto, ON: Canadian Cancer Society (Ontario Division), October 2007.
  3. Public Health Agency of Canada. Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Screening Program Performance - Second Edition. March, 2007. Available online at: (Accessed February 10, 2009).
  4. Canadian Cancer Society/National Cancer Institute of Canada. Canadian Cancer Statistics 2006. Special Topic: Progress in Cancer Control: Screening, p. 71-19. Available online at: February 10, 2009).



Changes Made


Type of Review (Formal Review or Ad Hoc)

Changes made by


June 2009

Formal Review

Cancer, Smoking and Sun Safety subgroup of Core Indicators.

  • A new section on the OPHS was included.
  • The indicator description was changed from 50-74 to 50-69 years of age to be in alignment with the Ontario Breast Screening Program's target age group.
  • The Method of Calculation was modified to exclude women who were screened for diagnostic reasons.
  • The analysis checklist was updated.
  • Information on the OHS will be posted on the OHS data source page and has not been included in this indicator because the OHS is older data. It may however, still be useful for historical comparisons.
  • All sections have been updated in alignment with the new Guide to Creating or Editing Core Indicator pages.

June 29, 2009

Ad hoc

Harleen Sahota on behalf of CIWG

  • Removed an out-of-date point in the Analysis Check List on how the Health Indicators department at Statistics Canada handles 'Not Stated' respondents when using CCHS data.
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