2.1 Search strategy

The search strategy was developed using a combination of key terms and synonyms for ‘colorectal cancer’, ‘screening’, ‘barriers’, ‘FOBT’, ‘Indigenous’, ‘disability’, ‘culturally diverse’, ‘LGBTQI’, ‘Low SES’ and ‘rural and remote’. Synonyms and spelling variations to represent the differences in specific American and English copy were included. For a full detail of the search strategy, see Supplementary Files. The final search strategy was adapted for Medline, Embase, Scopus, Cinahl, PsycInfo and Cochrane. Grey literature searches were conducted through Scopus, Google advanced search and by using the ‘snowball’ technique of searching bibliography lists of included references.

2.2 Inclusion and exclusion criteria

Studies were identified as eligible in this systematic review if they answered the research question by (a) including one or more of the identified priority populations impacted by the social determinants of health; (b) identifying empirical evidence contributing as a barrier to participation in FOBT CRC Screening; (c) utilising qualitative or mixed methodologies; (d) reporting original data. Articles were excluded from the systematic review if (a) barriers to screening could not be linked directly to patient experiences with FOBT testing; (b) studies did not contain the experiences and perceptions of at least one identified priority population; (c) quantitative study design only; (d) studies that did not include or report original data.

2.3 Data analysis

Studies were imported into Endnote where duplicates were removed before importing into COVIDENCE software for title and abstract screening. Data extraction follows meta-synthesis techniques by extracting findings from qualitative studies that answer the research question. This study objectively followed a 3-step approach involving meta-synthesis techniques to extract data through thematic coding, the development of a taxonomy of findings to demonstrate the conceptual range of data and the rendering of data to form new interpretations and theory. In line with Grounded Theory methodology, thematic coding and the development of new theory were created through the course of data extraction, memo writing and analysis, deriving new meaning and understanding of the phenomenon of equity and access to FOBT CRC screening for disadvantaged communities. In this study, coding has been applied in all instances when a barrier is disclosed by a participant from one of the identified priority populations. In some cases, community leaders' perceptions were included if they identified as belonging to one of the population cohorts under investigation.

2.4 Quality assessment/critical appraisal

Quality appraisal was conducted using the critical appraisal skills programme (CASP) where a 10-point check was conducted assessing quality of included qualitative studies using symbols (+/−) to demonstrate adherence to quality reporting of qualitative research. This tool was chosen due to its endorsement from the Cochrane Qualitative and Implementation Methods Group and due to the objective nature of appraisal. Two independent reviewers conducted the appraisal process with consensus reached on any variations in recorded assessment of study content.

2.5 Data extraction

Data extraction was coded inductively, line by line using NVIVO 12 PLUS Software. Two independent reviewers coded and cross-checked references for thematic relevance. During the initial phase of coding, memo writing was adopted to demonstrate the interconnectedness of themes and the thematical relevance and repetition among priority populations. During the second round of coding, thematic relevance was re-examined and cross-checked to ensure coded descriptive themes were conceptually ordered, representing distinguishable data. Codes were then grouped into higher order themes representing the key emergent findings from the cohort of included studies. When data were reported from mixed populations, clear identification of a priority population of interest had to be present with each statement for coding to be applied.

3.1 Search results

The search identified 8501 papers of which 2299 duplicate papers were removed using EndNote 20 software. The remaining 6202 papers were imported into COVIDENCE for Title and Abstract screening based on the selection criteria. Two independent reviewers screened articles for relevance with all discrepancies resolved by mutual discussion. Abstracts were eliminated in the initial screening if they used a quantitative only research design and did not report findings representing one or more of the identified priority populations. Full text of the remaining 197 papers were retrieved and reviewed against the full inclusion/exclusion criteria using the COVIDENCE voting system. Disagreements over the final study inclusions were resolved by a third-party neutral arbitrator. A total of 48 papers were included in this review of the literature. A flow chart of the study selection process is reported in Figure 1.^11-58

The basic characteristics extracted from the 48 included studies are presented in Table 1. Data on year of publication, country, aim, qualitative methodology, priority population and priority population sample size were all extracted using a customised Excel template. A total of 2232 subjects expressed barriers to FOBT based screening were included in the 48 studies across 10 countries. Population representation of included studies covered CALD (n = 32), Indigenous peoples (n = 6), disability (n = 2), Low SES (n = 3), rural/remote (n = 5) and LGBTQI+ (n = 0). Focus groups were the key method used to collect data and represented 52% of included studies, followed by a variety of semi-structured, in-depth and face to face interview formats.

3.2 Quality appraisal

Quality appraisal have been detailed in Table 2. Overall, 90% of studies were ranked between 8 and 10 (n = 43) on the CASP tool. The quality of transparent reporting was generally to a high standard, however some studies lacked methodological congruency and rigour of reporting. Reviewers reached agreement on most studies with areas of disagreements resolved through discussion.

3.3 Barriers to FOBT screening

Barriers to FOBT screening fell into 30 key descriptive themes with a thematic frequency greater than 10%. Themes translated further into four overarching, interconnected barriers driving inequality for priority populations: social, behavioural, economic and technology/interface barriers. No study represented data on LGBTQI+ populations specifically, however one disability focused study referenced this group as a population experiencing marginalization and barriers to screening extending beyond normative assumptions surrounding their bodies to presumptions on heteronormative sexuality. Bias and narrow perception on gender identification and sexuality for disabled communities were found to be deeply embedded in society.¹³ A full taxonomy of findings, including thematic frequencies is displayed in Table 3. Figure 2 continues to depict these frequencies further with one spike representative of each included study and the key barriers identified within each publication.

3.4 Social barriers

Social barriers were defined as community level barriers with strong associations to circumstances stemming from the social determinants of health and the collective elements shaping a participants' decision-making abilities. Social drivers and cultural influences such as beliefs in traditional healing and medicine, the taboo nature of talking about the colon or cancer and fatalistic attitudes were coded as the social barriers driving avoidance of participation in preventative screening.

Disengagement with health care and preventative FOBT CRC screening was another barrier associated with feelings of disempowerment at GP visits, medical mistrust, perceived discrimination/racism, and the belief that health care providers (HCPs) withhold valuable information. Medical mistrust was coded as a barrier to screening in 15 studies and was associated with episodes of trauma, perceived discrimination, racism or marginalisation. Participants frequently spoke of low self-advocacy or an inability to speak up and ask questions during HCP engagement, leaving participants feeling ill-informed on bowel cancer prevention and early detection. One Indigenous participant stated, ‘…and a lot of our Māori are frightened to ask questions…so they sit and they hear all these flash words and it can be quite intimidating…they fear that if they ask a question it will be considered a dumb question…So a lot of our people do sit there in a real whakama state [withdrawn] about even, you know, asking simple questions.’⁴⁶ Low satisfaction following medical visits in the absence of co-created experiences and decision making between patient and HCPs was also a common theme. This was particularly relevant to data coded from USA publications where federally organised CRC screening programs do not exist.

Complex sub themes surrounding shame for some culturally diverse groups was coded in 50% of included publications. Shame, embarrassment and discomfort stemmed from not only the social and cultural taboo and undesirable nature of dealing with faecal matter, to the perceived lack of privacy in homes for some Indigenous rural/remote participants.

While LGBTQI+ communities were not openly represented in any of the study yield, one participant expressed experiences of marginalisation around a physical disability and expressed difficulty accessing the health care system which was further compounded by heteronormative biases surrounding assumptions about sexuality and an inability to be truly ‘seen’ during HCP interactions.

3.5 Behavioural barriers

In this instance, behavioural barriers were identified as the personal beliefs/actions that shape decision-making abilities and choices surrounding health, on the individual level. Behavioural barriers included the sub-theme of only engaging in health care when sick, perpetuating the lack of engagement in preventative health services for priority populations impacted by the social determinants of health. This was characterised in the following statement from a paper representing rural and remote populations ‘We live in a rural area, so it's not a high priority as far… you know, if a person does not get sick to where they can work, they typically do not go to the doctor. You know we just do not run… preventative maintenance is not done here’.²⁴

Fear and its association with locus of control was thematically relevant in 60% of studies and commonly linked to statement surrounding fear or cancer diagnosis and beliefs that cancer cannot be cured or prevented. One participant stating, ‘I think—well from what a few people have said—and I think this is the general view of the Aboriginal community- that if you’ve got cancer you’re going to die so you just give up, there's no point [in undergoing CRC screening]’.⁵³

Low self-efficacy and the confidence in one's ability to successfully complete a FOBT was coded in 33% of included studies. Participants exploring this barrier within the included studies expressed difficulties around the screening modality, low confidence in their ability to use the FOBT and the need for additional support to successfully complete the kit.

3.6 Economic barriers

Economic barriers have been defined as financial and infrastructure barriers that impede a person's ability to act on decisions that will positively impact their health. Information asymmetry is an economic phenomenon that describes a circumstance where one party holds greater power or benefit as a result of holding a higher level on knowledge or information over another party. Information asymmetry and lower levels of general knowledge and awareness on FOBT based CRC screening was coded as a barrier in 92% of included studies (n = 44). This lack of understanding relating to FOBT CRC screening was a perpetual economic driven denominator contributing to low-risk perceptions throughout synthesised studies and included all population groups.

Lack of knowledge about CRC was further expressed by many CALD and Indigenous peoples with the belief that they were protected as a virtue of race. CRC was frequently cited as a western disease and not something that affected their people. One participant from a study of Indigenous people stated, ‘I’ve never thought of it this way, but I’ve been told that many Native American populations just don’t think that Native Americans get cancer, because the statistics are so low…and I don’t think that a lot of times their healthcare providers or their rural locations have all the information necessarily to provide’.²⁴ Participants stated that CRC is not often discussed within communities, and there is little education infiltrating cultural and behavioural norms or within the limited time allocations in GP visits.

Further economic barriers to FOBT based screening included the need for financial support to complete the screening process and taking unpaid time off work.^{12, 13, 20-22, 27, 29-31, 52}

3.7 Interface/technological barriers

Interface or technological based barriers were coded when a system-based barrier was identified as impeding the ease of access to FOBT screening. Kit aesthetics, lack of cultural support/cultural competency, complexity of languages on FOBT kit/instructions and language barriers with HCPs contributed significantly to the accessibility and equitability of CRC screening.

Language barriers extended past participants of Non-English-Speaking backgrounds (NESB) and CALD groups to Rural and Remote and Low SES communities. Language barriers and the need for translational assistance to enable participation was a result of medical jargon, confusing instructions and language discordance. If a support person perceived the kit as being of low importance, then a participant's opportunity to complete the preventative health action was compromised. This was cited in papers representing both CALD and disability groups and is embodied in the following quote, ‘She [my mum] said to me, there's a letter for me from the doctor. I came and looked at it but I didn’t put that much emphasis on the importance, I didn’t encourage her to take up’.⁴⁴ Similarly, the need for physical assistance to complete the stool sample was coded for people with a disability. This, along with co-morbidities and lack of HCP support contributed further to feelings of disempowerment and inaccessibility to FOBT screening. Unmet patient navigation needs and the requirement for additional support was thematically relevant in 46% of included studies and spanned across all included population groups.

3.8 Interpretation

To our knowledge, this is the first qualitative systematic review to assess the empirical evidence surrounding barriers to FOBT CRC screening for populations impacted by the social determinants of health.

Consistent with past quantitative and mixed method reviews, behavioural and economic barriers such as low health literacy and low utilisation of health care due to past negative experiences is typical for populations impacted by social and economic disadvantage. Our study findings highlight that in the absence of both health literacy and strong patient/HCP relationships, a person's ability to access, process, perceive value and act on health information to enhance wellbeing, is compromised.

Participant statements surrounding the inherent need for support and patient navigation to enable equitable access to screening was echoed across all priority population groups. Consumer driven solutions that aim to mitigate fear-based beliefs and social/cultural norms is one way to increase the value placed on the lifesaving abilities of FOBT based screening.⁹ Similarly, findings from a recent review of the Australian National Bowel Cancer Screening Program emphasise the potential for additional patient navigation and support to increase participation and the accessibility of FOBT screening for various population groups.

The identification of asymmetric information as one of the leading drivers of inequalities in FOBT based CRC screening was a novel interpretation of findings in this review. Information asymmetry occurs when one party has better quality information than another party, posing a serious threat to risk perceptions and perceived health care value for some groups.⁵⁹ In the instance of FOBT based screening, the power imbalance seemingly exists due to the language HCPs and governments use when promoting participation in FOBT based CRC screening. While this language may be useful and increase value perceptions and participation within the general population, it proves to create a power imbalance and further barriers to access for diverse groups. The engendering of inaccessibility to screening from a policy/system level in combination with the stresses and complexities of everyday living, placed screening as a low priority for many groups within the included studies. Consumer value creation can be achieved when gaps in knowledge, locus of control and self-efficacy are addressed, and wellbeing outcomes are realised for a consumer.⁶⁰ Without the consideration of populations experiencing inequality in the accessibility of preventative health services, we run the risk of increasing the social gradient and the disparities between good health and poor health between populations. Addressing social justice and health equity, requires extending the success of CRC screening to diverse populations. An auspicious environment to enhance the potential of FOBT based CRC screening seemingly exists within the patient/doctor relationship. Enabling diverse communities to see the value in screening through education and knowledge has the potential to break down many of the barriers identified within this review of the literature. To ignore the inclusion of priority populations in policy and system level planning is to deny the full economic and population wide potential of screening for CRC through FOBT.

We anticipate that these findings will be equally relevant for a range of stakeholders including policymakers, physicians and public health workers who are invested in increasing the equitability and accessibility of CRC screening throughout all levels of policy, planning, implementation and evaluation.

3.9 Limitations

This systematic review is the first to focus on the qualitative evidence surrounding the barriers to FOBT screening for priority population groups. Some limitations to the study methodology and data synthesis may exist. A methodologically rigorous approach was adopted throughout the search strategy, however, there is still a risk that some publications may have been missed. We utilised the support of a highly skilled medical librarian to review our search strategy and results to help mitigate this concern. Further limitations exist in the relatively small number of publications across each respective population group with CALD groups heavily saturating data findings. Groups such as LGBTQI+, disability and rural and remote have contributed significantly less to the overall study findings and may have added further to the system level or technology-based barriers to accessing CRC screening. Finally, this qualitative systematic review was limited to study findings published in English.