How is equity captured for colorectal, breast and cervical cancer incidence and screening in the Republic of Ireland: A review

Highlights • Incidence of breast, cervical and colorectal cancer and participation in screening varies across subgroups in Ireland.• Place of residence, socio-economic position, sex, and age were the most frequently captured stratifiers.• PROGRESS-Plus is a useful equity lens to review health literature.• Implementation of unique health identifiers would enhance equity monitoring and evidence-based promotion interventions.• Collaboration with organisations who work with underscreened populations would support understanding of non-participation.

Introduction: Organised screening reduces the incidence and late-stage diagnosis of cancer.However, participation in screening is not consistent across populations.Variations can be measured using demographic factors on place of residence, race/ethnicity, occupation, gender/sex, religion, education, socio-economic position (SEP), and social capital (PROGRESS-Plus stratifiers).The Republic of Ireland has screening programmes for colorectal, breast, and cervical cancer but assessment of screening participation and cancer incidence is inconsistent.The review aimed to evaluate the use of stratifiers in breast, cervical and colorectal cancer incidence and screening literature, and assess variations in incidence and screening participation across subgroups in Ireland.Methods: PubMed was searched systematically and grey literature was identified via Google, Google Scholar, Lenus (Irish Health Research repository), and The Irish Longitudinal Study of Aging (TILDA) in June 2022.Studies were included if they captured stratifiers alongside incidence or screening participation data of the three cancers.Results: Thirty-six studies and reports were included.Place of residence, SEP, sex, and age were most frequently captured.Incidence and screening participation varied by age, place of residence, SEP, and sex.Discussion: PROGRESS-Plus is a useful equity lens to review health literature.Cancer incidence and screening participation studies lacked a comprehensive equity lens resulting in difficulties in identifying inequities and non-attenders.Place of residence, SEP and ethnicity should be prioritised in monitoring inequities.Integrating unique health identifiers should improve monitoring and enable evidence-based population-specific interventions to promote screening.Collaboration with community organisations would support engagement with vulnerable populations when data is limited.

Incidence of colorectal, breast and cervical cancer and participation in cancer screening
Europe accounted for almost a quarter (22.8%) of all cancers globally (World Health Organisation, 2020) and incidence is projected to rise over the coming decades (European Commission).In Europe, breast cancer is the most common cancer among women.Bowel cancer is the 3rd most common cancer and 2nd leading cause of cancer-related death for men and women in Europe.Cervical cancer is the 11th most common cancer for women.The incidence of these cancers varies across demographics such as age, sex, place of residence, socio-economic position and ethnicity (Buskwofie et al., 2020;Coughlin, 2019;Coughlin, 2020).The EU Beating Cancer Plan aims to reduce the burden of cancer and strive for equitable care across Europe (European Commission, 2022).
Cancer screening plays a key role in early identification of cancer and its pre-cursors, reducing morbidity and mortality (Raffle et al., 2019).Organised screening programmes invite certain groups in the population at intervals, based on evidence, to prevent or detect cancer early to reduce population morbidity cost-effectively (World Health Organisation, 2022).Alternatively, opportunistic screening is ad-hoc, relying on the individual to participate in screening.Differences in participation across subgroups in a population are lessened with organised compared to opportunistic screening (De Prez et al., 2022;De Prez et al., 2021).As with cancer incidence, participation in screening varies by demographic characteristics as well as contextual factors, such as family or provider recommendation and distance to the screening service (Rollet et al., 2021;Smith et al., 2019).
The EU recommends organised programmes for breast, colorectal and cervical cancer screening.The Republic of Ireland (Ireland) has three cancer screening programmes that are free to eligible populations: BowelScreen is available every two years to anyone aged between 60 and 69 (established in 2012); BreastCheck screens women aged 50-69 every two years (established in 2002); and CervicalCheck is available to people with a cervix aged 25-29 every 3 years and every 5 years to those aged 30-65 (established in 2008).

Measuring equity
Equity relates to fairness in health and can be defined as 'the absence of health disparities (and in its key social determinants) that are systematically associated with social advantage/disadvantage' (Braveman and Gruskin, 2003) (p256).Inequity within this review refers to unfair disparities while inequality refers to differences in health across population groups (Arcaya et al., 2015).The social determinants of health consist of social, environmental, living and working conditions, social networks and individual lifestyle factors that influence access to healthcare and health outcomes (Dahlgren and Whitehead, 2021).Similarly, Cochrane PROGRESS-Plus is a list of factors that influence health called equity stratifiers.This includes: place of residence, race/ethnicity/culture/ language, occupation, gender/sex, religion, education, socioeconomic position (SEP), social capital, and other characteristics including age, sexual orientation, disability, behaviours and relationships (Cochrane;Kavanagh et al., 2008).PROGRESS-Plus can be applied as an equity framework in health research (O'Neill et al., 2014).
There is an international push to understand and address equity in health (European Commission, 2022;World Health Organisation, 2017).Monitoring health data can identify changes across the life course, enable comparisons across regions, identify disparities in health status, needs and access, and resource management (Tulchinsky and Varavikova, 2014).

Equity in the Irish context
Ireland has a mixed public and private health system.Some health services, such as GP consultations, incur fees and without a medical card (a means-tested entitlement to free public health services based on income, age, and health status) or private health insurance cover these are paid out-of-pocket.People who do not have proof of ordinary residence of at least 12 months, e.g., new migrants, are not eligible for medical cards or other entitlements regardless of income or health status.People of lower SEP and born outside of Ireland have lower life expectancy (Duffy et al., 2022).Over one-quarter of people in Ireland have limited health literacy and navigating the system can be challenging, especially for those with health conditions (National Adult Literacy Agency, 2020).The Health Service Executive (HSE) work with several vulnerable populations: people facing addiction, homelessness, domestic violence, intercultural communities, Irish Travellers and Roma populations, and lesbian, gay, bisexual, trans, queer, intersex people (LGBT+) (Health Service Executive, 2023).Recent health policies for vulnerable populations recognise the need for reform for appropriate care provision to address poorer health outcomes and inequitable access to services (Department of Health, 2022;Department of Housing Local Government and Heritage, 2016;National Social Inclusion Office, 2018; Policy Drugs Unit Social Inclusion, 2020; The Department of Justice and Equality.The Department of Justice and Equality, 2019).Irish Travellers, an ethnic minority population, exemplify a population with specific needs as they face discrimination in employment, housing and health service utilisation, as well as having poorer health outcomes (All Ireland Traveller Health Study Team, 2010;Department of Health, 2022).Additionally, the homeless population often have complex physical and mental care needs and struggle with addiction, have limited access to appropriate care, delay seeking care and rely on emergency services (Ní Cheallaigh et al., 2017).Sláintecare is a cross-party consensus health policy to reform the health system that strives for equitable, patient-centred, universal healthcare (Houses of the Oireachtas Committee on the Future of Healthcare, 2017).Slaintecare seeks to address the social determinants of health where patients are treated based on need rather than ability to pay and prevention and health promotion core tenets (Houses of the Oireachtas Committee on the Future of Healthcare, 2017).
Key to addressing the social determinants of health is measuring them.A recent study investigated what PROGRESS-Plus stratifiers were collected across health and social care data collections in Ireland (Carroll et al., 2021).Twenty-nine data dictionaries were included.Age, sex, place of residence and SEP were captured frequently, ethnicity, education, disability and sexual orientation less so.The Pobal HP Deprivation Index was the most commonly used measure for SEP which is a composite measure based on Central Statistics Office (CSO) area-level demographics that measures area-level population (not individual) affluence and deprivation (Haase and Pratschke, 2016).Overall, Ireland has limited means to capture equity, therefore synthesising literature is required to gain a clearer picture of health equity.

Aims
This study aimed to conduct a rapid review using a systematic approach to: (1) Evaluate the use of equity measures in cancer incidence and cancer screening reports and quantitative studies in Ireland.
(2) Assess variations in incidence of colorectal, breast and cervical cancer across subgroups of the Irish population.
(3) Assess variations in participation in colorectal, breast, and cervical screening across subgroups of the Irish population.

Materials and methods
We conducted a systematic search of PubMed to identify peerreviewed studies that address the aims of the review.We included grey literature such as needs assessments and reports from nongovernmental organisations, the National Screening Service (NSS), National Cancer Registry Ireland (NCRI), and Central Statistics Office (CSO) regarding screening for colorectal, breast and cervical cancer.
We devised search strategies in PubMed for the three conditions on incidence and screening participation in Ireland, totalling six search strategies.The searches contained keywords including 'colorectal cancer', 'breast cancer', 'cervical cancer', 'incidence', 'screening', 'participat*', 'attend*', 'coverage', 'uptake', 'engage*', 'utilis*', 'non-attend*', 'non-respon*', and 'Ireland', utilising the MeSH terms and title and abstract functions (Supplementary material 1).We did not limit the searches by time frame or language (Table 1).We ran the searches between May and June 2022.The most recently published NSS reports on screening participation, NCRI reports on cancer incidence and CSO health survey reports were deemed to have the most up-to-date information from these organisations and to provide the current baseline population-wide measures of screening participation and cancer incidence.We searched for additional literature and reports via Google, Google Scholar, and Lenus (Irish Health Research repository) searches, The Irish Longitudinal Study of Aging (TILDA) (a nationally representative longitudinal study) publication search tool and by reviewing the reference lists of the included sources.
We included studies and reports if they; a) measured incidence of breast, cervical or colorectal cancer or b) measured breast, cervical or colorectal cancer screening participation; in the Republic of Ireland and; collected or reported PROGRESS-Plus stratifiers (Table 1).We excluded studies if they did not quantitively report on participation in breast, colorectal or cervical cancer screening; did not report incidence or screening participation in relation to any stratifier; were not in Ireland or segregated data on Ireland were not reported.
We downloaded search results into an Excel file.The lead authors screened titles and abstracts in Endnote 20 and tagged studies for inclusion or exclusion in an Excel file.SMS downloaded and screened full texts of the relevant studies.Uncertainties of inclusion or exclusion were resolved amongst the authors.We extracted data pertaining to peerreview status, study design, population, aims, methods, condition, use of stratifiers and results relevant to the research question into an Excel file (Supplementary material 2).PL extracted data for 20% of the included literature to check for concordance, of which there was high agreement.We synthesised studies narratively and categorised them by cancer type and incidence or screening participation, noting which PROGRESS-Plus equity stratifiers were used.A meta-analysis was not conducted due to the heterogeneity of data collection and analysis.SMS, appraised all peer-reviewed studies for quality using the Mixed Methods Appraisal tool (MMAT) (Hong et al., 2018), which appraises the appropriateness of methods for the research question, sample, measurements used, risk of bias and analytical methods of empirical studies for systematic reviews that include a variety of study types.For the quality appraisal of grey literature, Authority, Accuracy, Coverage, Objectivity, Date and Significance tool (AACODS) was used (Tyndall, 2010).

Critical appraisal
The majority of included studies were of high quality (Supplementary material 3).All grey literature was from reputable sources with clear aims, objectivity, and significance, however details of methodologies were often limited.Peer-reviewed studies were mostly of high quality.Some studies lacked transparency regarding the representativeness of samples, methodology or risk of non-response bias.No studies were excluded due to low quality.

Use of equity stratifiers
The use of PROGRESS-Plus stratifiers varied widely.Sex, place of residence and SEP were the most commonly captured stratifiers, while religion was only captured in one study (Fig. 2; Tables 3a; Table 3b).Age was the most frequently captured stratifier.Some studies captured other stratifiers such as disability, sexual orientation, possession of private health insurance or a medical card.Incidence studies only used age, sex, place of residence and SEP stratifiers.Screening participation studies covered a broader range of stratifiers.Several studies measured SEP by the Pobal deprivation index, or otherwise occupation or area-based unemployment status (Donnelly et al., 2013;Sharp et al., 2014;Walsh et al., 2012).Despite capturing stratifiers, they were not always applied to determine variation across the population.

Socio-economic position.
Area deprivation was used to measure SEP.One study found a weak association with more deprived areas and higher incidence of colorectal cancer in males only (Donnelly et al., 2013).In another study, an association was only seen among urban males who showed significantly higher incidence in more deprived areas (13%), this association was not evident among females or in rural areas (Walsh et al., 2016).

Breast cancer
The average age-standardised incidence rate for female only breast cancer was 121.6 per 100,000 (National Cancer Registry Ireland, 2022a).All studies reported data for female breast cancer.

Age.
Incidence of breast cancer increased significantly with increasing age, the median age group according to NCRI was 60-64 years (National Cancer Registry Ireland, 2022b).The association between older age and higher incidence of breast cancer was evident in all three studies that reported on it (National Cancer Registry Ireland, 2022a, b;Walsh et al., 2016).

Place of residence.
The counties with the highest standardised incidence rate (1.06-1.15)were Leitrim and Cork (National Cancer Registry Ireland, 2022b).Incidence was higher in urban areas (Sharp et al., 2014;Walsh et al., 2016).

Socio-economic position.
Women from the least deprived areas were more likely to be diagnosed with breast cancer (Donnelly et al., 2013;Walsh et al., 2016).One study determined that differences in breast cancer incidence between most deprived and least deprived areas were greater in urban compared to rural areas (Walsh et al., 2016).

Cervical cancer
The average age-standardised incidence rate for cervical cancer was 11.3 per 100,000 between 2017 and 2019 (National Cancer Registry Ireland, 2022a)..4.3.1. Age.Women between 25 and 59 had higher incidence at 19.1 per 100,000 compared to older age groups (National Cancer Registry Ireland, 2022a) with the majority of cases occurring under 50 years of age and the median age group was 45-49 (National Cancer Registry Ireland, 2018a;O'Brien and Sharp, 2013;Walsh et al., 2016).

Place of residence.
The counties with the highest standardised incidence rate of 1.16+ per 100,000 were Westmeath, Laois, Offaly and Wexford (National Cancer Registry Ireland, 2018a).Incidence was higher in urban areas (Sharp et al., 2014;Walsh et al., 2016).

AACODS, high
strongest association with area deprivation compared to the other cancers, with incidence nearly double in the most compared to least deprived areas (O'Brien and Sharp, 2013;Walsh et al., 2016).One study found differences between most deprived and least deprived areas were greater in urban compared to rural areas (Walsh et al., 2016).One study used the medical card as a variable to explore incidence on cervical cancer and found that medical card holders had higher incidence of the disease, although it was not statistically significant (O'Brien and Sharp, 2013).
*The Pobal index uses demographic profile, social class composition and labour market status from census data to create a standardised measure of deprivation in small areas in Ireland.+ Medical card is a means-tested entitlement to free public health services based on income, age, and health status.
Fig. 2. Use of equity stratifiers in included literature.SEP = Socio-economic position.Sex was only collected in colorectal cancer studies where screening is offered to males and females, gender identity was not captured.

Use of other stratifiers in incidence differences
No studies or reports analysed the association of ethnicity, religion, education, occupation or social capital on breast, cervical and colorectal cancer incidence.Equally, none captured data on the Traveller population, people with disabilities, homeless people, or the LGBT+ community.

Participation results
Variations in participation are summarised in Table 4.

Colorectal screening
Colorectal screening participation of the eligible population was 41.9% in the 2018-2019 interval, and has steadily increased since it was introduced in 2012 (National Screening Service, 2020a).
3.5.1.1.Sex.Men were less likely than women to participate in colorectal screening (Clarke et al., 2016;McNamara et al., 2014;McNamara et al., 2011). 3.5.1.2.Age.Men and women in the older age bracket (65-69) eligible for screening had lower participation rates for colorectal screening in one report (National Screening Service, 2020a).However, two studies found older age was associated with higher participation (Clarke et al., 2016;McNamara et al., 2014).Older age also contributed to reduced likelihood of return to colorectal screening after false-positive results compared to individuals with negative results (Ch'ng et al., 2019).

Place of residence.
No data were available on county-level differences (National Screening Service, 2020a) or urban-rural place of residence.

Socio-economic position.
There was an association between deprivation and participation, whereby participation was higher in least deprived areas in one area in Dublin (Clarke et al., 2016).Higher income, higher SEP, and having private insurance were associated with greater participation before the national programme was implemented (Walsh et al., 2012). 3.5.1.5. Ethnicity.A study conducted among the Traveller community living in County Clare reported 4.3% participation of colorectal cancer screening in the previous 12 months (Pavee Point Traveller and Roma Centre & Mid West Traveller Health Unit, 2019).No other studies reported on ethnicity.

Use of other stratifiers.
No studies reported on differences in participation of colorectal screening by occupation, education, religion, or social capital.

Place of residence.
All counties reached at least 70% participation over the 2018-19 interval for breast screening (National Screening Service, 2020b).A 2019 CSO survey reported that selfreported participation in the last 12 months, adjusted to represent the population over 15 years old, was lowest in Border and West regions (11%) and highest in South-East (15%) (Central Statistics Office, 2020).In another study, living in Dublin was associated with increased likelihood of participating compared to rural areas or other towns and cities (Connolly and Whyte, 2019).Similar urban-rural differences were evident in a study on previous non-attenders of breast screening (Fleming et al., 2013).In contrast, a study from 2011 using the first wave of TILDA data, reported women (aged 50+) in rural areas were less likely to have a mammogram than urban women (Barrett et al., 2011). 3.5.2.3. Socio-economic position, education, occupation.The CSO reported mammogram self-reported participation in the last 12 months at 13% for employed women compared to 6% among unemployed women but no difference by area deprivation (Central Statistics Office, 2020).The odds of participation in breast screening increased with higher educational attainment, higher income, and higher SEP (Barrett et al., 2011;Connolly and Whyte, 2019;Walsh et al., 2010Walsh et al., , 2012)).

Ethnicity.
A minor difference was evident between Irish (13%) and non-Irish (10%) nationality for self-reported participation at breast screening in the CSO survey (Central Statistics Office, 2020).
In a 2019 needs assessment of Travellers living in Clare, 16% selfreported breast screening participation in the last 12 months; this was lower than the comparable 2010 AITHS study of 25% (All Ireland Traveller Health Study Team, 2010;Pavee Point Traveller and Roma Centre & Mid West Traveller Health Unit, 2019).
3.5.2.5.Use of other stratifiers.Participation increased for women with private medical insurance (Connolly and Whyte, 2019;Moore et al., 2017;Walsh et al., 2012).Possession of a medical card reduced participation in screening but possession of both a medical card and private health insurance was associated with higher participation in another study (Connolly and Whyte, 2019;Moore et al., 2017).
The odds of participation in breast screening were higher for married women and those in good health (Connolly and Whyte, 2019).
Two studies that investigated intellectual disabilities in Ireland found that participation was lower than the general population and participation decreased with more severe disability (Lalor and Redmond, 2009;McCarron et al., 2011).
Social capital was captured only by marriage.Religion was the only equity stratifier not captured.

Cervical screening
Cervical screening participation of the eligible population was 78.7% during the 2015-2020 screening interval (National Screening Service, 2022)..5.3.1. Age.Of the eligible population, younger women had the highest participation in the 5-year period 2015-2020, which declined with increasing age (50-54, 71%; 55-59, 67%; 60+, 59%), a trend visible since the introduction of the cervical screening programme in 2008 (National Screening Service, 2022).A study in one general practice corroborated this finding with women aged 25-44 having highest participation in screening (Gallagher and Gallagher, 2010).

Place of residence.
Counties Laois and Kilkenny had the lowest participation rate for cervical screening at 69%, while Clare, Dublin, Monaghan and Roscommon all had participation below 75% in the 2015-2020 interval (National Screening Service, 2022).No data were found on urban-rural place of residence and cervical screening participation.The 2019 CSO Health Survey found lowest self-reported cervical screening participation in the last 12 months, among the population over 15 years old, in the South-East (15%) region for cervical screening compared to the highest rates in Dublin (23%) (Central Statistics Office, 2020).education,occupation.Most studies that analysed socio-economic variation pre-date the establishment of CervicalCheck.Participation varied by education, whereby women with lower levels of educational attainment had lower participation (Walsh et al., 2010(Walsh et al., , 2012)).In one study where occupation was used to measure SEP, lower SEP had lower odds of participation (Walsh et al., 2010).Higher income, higher SEP, and having private insurance were associated with greater participation in screening (Walsh et al., 2012).In another study, participation increased with higher SEP in the GP patient population (Ní Riain et al., 2001).Participation in the last 12 months was lower in the most deprived compared to least deprived areas among the population over 15 years old (Central Statistics Office, 2020).

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3.5.3.4.Ethnicity.Twenty-seven percent of non-Irish women reported having cervical screening in the last 12 months compared to 19% of Irish women in the CSO report that surveyed people aged 15+ (beyond the eligible screening age) (Central Statistics Office, 2020).
In another 2019 study, self-reported cervical screening participation in the last 12 months among Travellers in Clare was high and remained the same as the 2010 AITHS at 23% (All Ireland Traveller Health Study Team, 2010; Pavee Point Traveller and Roma Centre & Mid West Traveller Health Unit, 2019).

Use of other stratifiers.
In a study conducted with the LGBT+ community, 66% of respondents said they attended every time they were invited (i.e., every 3-5 years), lower than the national rate of 78%.20% reported that their last test was over 5 years ago or they had never been screened (National Screening Service, 2021).
No studies analysed participation of cervical screening by religion or social capital.No studies investigated non-attender demographics for cervical cancer screening.

Discussion
This review evaluated the use of PROGRESS-Plus stratifiers in breast, cervical and colorectal cancer incidence and screening participation literature and mapped differences in incidence and screening participation across subgroups in Ireland.PROGRESS-Plus was a useful framework to monitor health equity.The findings highlight a limited use of stratifiers and variations in methodologies, resulting in difficulties determining true subgroup differences in screening participation.

Measuring equity in cancer incidence
Incidence studies captured a limited set of stratifiers to understand subgroup differences in colorectal, breast and cervical cancer.Sex, age, place of residence and SEP were the only demographics used to explore inequities and was limited to data from the National Cancer Registry.The results from this review are comparable to trends in variation by SEP (Hiscock et al., 2012;Mihor et al., 2020) and urban areas (Carnegie et al., 2022).Despite male breast cancer being rare, it is important to capture sex to ensure the needs of this underserved population can be met (Fentiman, 2018).Late stage diagnosis and increased mortality is evident for those in more deprived areas in colorectal, breast and cervical cancer adding to disparities (Bambury et al., 2023;Walsh et al., 2016).Consistent measurement of sex, SEP and place of residence in relation to incidence and other outcomes would support resource allocation required for equitable access to care.

Measuring equity in cancer screening participation
Studies and reports varied widely in capturing screening participation.Some studies used convenience sampling, others had nationally representative samples or used the screening registry data, this limited the ability to compare results as some were prone to selection bias.Future research would benefit from standardising reporting participation in line with the screening intervals, ideally linking to screening registry data rather than using self-report data as recall bias influences the accuracy of the results.
Variations across stratifiers was more broadly captured in participation literature but poorly captured for non-attender demographics.Breast screening was most commonly studied and comprised the widest use of equity stratifiers.Screening registry data is limited to age, sex, and county level stratifiers and would benefit from including SEP and ethnicity stratifiers.The trends in screening participation align with international studies where education, age, income, place of residence, and disability are all determinants (Carrozzi et al., 2015;Dugord and Franc, 2022;McCowan et al., 2019;Mihor et al., 2020;Walji et al., 2021).The lower participation of men in colorectal screening is evident internationally (Clarke et al., 2015).We postulate whether women's engagement with breast and cervical screening raises their engagement with colorectal screening compared to men.High participation, particularly cervical screening, among Travellers was attributed to primary healthcare projects and community health workers (Department of Health, 2022).LGBT+ participation was lower than the national average, likely an underestimate given the sample had few older women and people with lower educational attainment; the main barriers to participating include heteronormative assumptions being made by healthcare professionals and fear of the test procedure (National Screening Service, 2021).In one study, non-Irish women were identified as having higher levels of participation in cervical screening, contrary to most research that indicates participation varies due to cultural differences in attitudes and access to care by ethnicity and migration status (Anderson de Cuevas et al., 2018;Marlow et al., 2015;Tatari et al., 2020).It is not clear what the reason for this result is, however cultural norms where women may get screened annually go for private screens with gynaecologists or attend in their home countries could be a factor (Marques et al., 2020;Marta et al., 2012).Further work should identify non-attenders, their barriers and enablers to participation, and intersectional interactions between stratifiers.

Enhancing monitoring of cancer incidence and screening participation data
Digital health monitoring is needed to reduce inequities in mortality and morbidity of cancer.As part of the EU Beating Cancer Plan, a cancer inequalities registry has been created to track variations across countries but is only as good as the data they receive (European Commission, 2022).The HSE are striving to enhance ethnicity monitoring across health services and the NSS are planning to introduce geo-coded data to the screening registry.Individual health identifiers, initially recommended over ten years ago, are vital to integration of health information systems and plans are underway to implement them in screening registries (Health Information and Quality Authority, 2011).These are valuable but small steps towards improved monitoring.Ireland has strategies to improve information systems, however implementation has been difficult due to resourcing issues and political pressure is required to enable whole system changes (Health Service Executive, 2013, 2015;Walsh et al., 2021).Countries such as Scotland and Denmark have systems to monitor health, collect equity stratifers and are used in planning and research (Walsh et al., 2021).The World Health Organisation provide a 5-step manual for best practice in managing health inequalities: 1) determining the scope of monitoring, 2) obtain data, 3) analyse data, 4) report results, 5) implement changes (World Health Organisation, 2017).The manual provides a framework to support Irish and other health systems experiencing shortcomings in digital transformation and facilitate cross-country comparisons.
Equity-focused research will provide evidence to address inequities in health outcomes, service provision and access.PROGRESS-Plus captured the social determinants of health well and has scope to capture determinants specific to Ireland including medical cards, private health insurance, and determinants relevant to vulnerable populations.Understanding the needs of vulnerable groups who have more issues accessing services can determine where inequities exist.Indeed, some literature included in this review conducted research with vulnerable groups (All Ireland Traveller Health Study Team, 2010;National Screening Service, 2021;Pavee Point Traveller and Roma Centre & Mid West Traveller Health Unit, 2019).This work could be replicated with other groups who have typically lower participation in screening and engagement with other health services.Qualitative research would be valuable in determining factors influencing non-participation, beliefs and attitudes towards cancer and screening.Other underlying social determinants of health not captured in PROGRESS-Plus, such as cultural influence, knowledge, or practical constraints (e.g.neighbourhood facilities, access to services), contributing to participation would be illuminated in qualitative research and theory (Chorley et al., 2017;Le Bonniec et al., 2023).The qualitative study excluded at full text in this review found differing influences of participation in older and younger women using behaviour theory framework to contribute to developing population-specific interventions (O'Donovan et al., 2021).There is a plethora of intervention studies that effectively promote screening among underscreened populations that provide insights on engagement with these populations (Cullerton et al., 2016;Dietrich et al., 2006;Dunn et al., 2017).Efforts should focus on research with stakeholder engagement and collaboration with community organisations to develop evidence-based interventions for underscreened populations.

Limitations
This review was conducted rapidly as part of research to inform the development of a strategic framework to improve equity in screening for the National Screening Service (unpublished) due to time and resource constraints.Hence, only one database was searched and there was limited consultation with stakeholders to identify other relevant literature.Screening and cross-checking data extraction by multiple authors was completed for a sample of all included literature, potentially missing evidence valuable to the review.Meta-analysis was not possible because the included data was not compatible with this approach.Some included studies predated the introduction of the screening programmes, therefore stratifiers influencing participation may have changed since then.This review excluded qualitative studies, exploration of the barriers and facilitators influencing participation in screening was not possible.

Conclusion
Gaps in the measurement of equity for breast, colorectal and cervical cancer incidence and participation in screening were identified.PROGRESS-Plus is a useful equity lens to review health literature.Particular attention should be paid to consistently monitoring place of residence, ethnicity, and SEP while efforts should be made to capture lesser used stratifiers.Implementation of unique health identifiers and integration of health datasets is required to progress equity of access to care and cancer outcomes.Moving away from self-reported data on screening and linking screening registry data to uncover variations across stratifers would enhance evidence to prioritise resources and implement tailored interventions that promote screening where it is needed.Qualitative research would shed light on underlying influences of participation, beliefs and attitudes towards cancer and screening.Leveraging relationships with community organisations may support understanding of challenges within specific non-attender populations who are hard to engage with.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Table 1
Inclusion and exclusion criteria.

Table 2
Summary of included literature.
(continued on next page) S. Mulcahy Symmons et al.

Table 2
(continued ) Table of use of equity stratifiers in screening participation studies by cancer type.

Table 3b
Table of use of equity stratifiers in screening participation studies by cancer type.

Table 4
Variations in incidence and screening participation by PROGRESS-Plus Stratifiers.