Community Health Workers for Primary Healthcare Access (COMPASS), integrating a comprehensive CHW intervention in primary healthcare in Belgium: a cluster-randomized controlled trial protocol

Abstract

Background

Inequality in access to Primary Health Care (PHC) is increasing in Belgium, in contrast to an overall decreasing trend throughout the European Union. A (cost-)effective solution for access-to-care challenges for people who experience challenges accessing primary healthcare (PECAP) in Belgium is needed; to address this knowledge gap, the research team drew on lessons from the CHW model in the Family Health Strategy (Brazil) and Re-engineering PHC (South Africa), in line with reciprocal innovation, to develop the Community Health Workers for Primary Healthcare Access (COMPASS) intervention.

Methods

The COMPASS study is a cluster-randomized controlled trial (cRCT) in the city of Antwerp, Belgium. Eighteen general practitioner (GP) practices are randomly allocated to the intervention or control arm. In each GP practice, we aim to enrol 21 PECAP, resulting in a total of 378 adult PECAP in the cRCT. Recruitment of study participants commenced on November 28th, 2024, and was completed by June 11th, 2025. In the control arm, participants will receive standard care. In the intervention arm, CHWs will offer a comprehensive package of support in addition to the current standard of care to an individual living in socio-economically vulnerable circumstances during home visits over the course of 12 months.

A longitudinal mixed methods design is adopted. To assess the effectiveness of the cRCT, methods including cluster-level analysis as well as linear and generalized linear mixed models will be used. The primary study outcomes of the quantitative research will comprise self-perceived health. Secondary outcomes include health care use, health-related quality of life, health literacy, empowerment, and financial burden of health care. An economic evaluation alongside the cRCT will be conducted to assess the cost-effectiveness of the intervention in addition to usual care, compared to standard care alone. To assess the acceptability and feasibility, as well as the underlying mechanisms of the impact on access to care, qualitative data (in-depth interviews, focus group discussions, and participant observations) will be collected at two time points.

Discussion

Via a comprehensive CHW intervention in collaboration with GP practices, the COMPASS cRCT aims to provide crucial evidence on the (cost-)effectiveness, acceptability, and feasibility of an intervention delivered by CHWs linked to GP practices in communities with PECAPs in Belgium. If proven effective, this model may offer a scalable strategy to mitigate healthcare access disparities across Belgium.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-025-09205-x.

Introduction

Background and rationale (SPIRIT point 6a)

While access to Primary Health Care (PHC) is essential for population health and wellbeing, there is nevertheless a high percentage of people who experience challenges in accessing PHC (PECAP) in Belgium. Research has demonstrated that PECAP in Belgium predominantly comprise people who live in socio-economic difficulties and/or have a low educational attainment [1]. PECAP are most often in need of care but are among the least likely to receive it [2]: people with a low educational level are four times more likely to postpone care than those with the highest level of education. Regarding income, the differences are even more pronounced: the proportion of individuals reporting postponement of care equals 6.7% for people in the lowest income quintile versus 0.0% for the highest [3]. Overall, 27% of people within the most vulnerable social group do not seek medical care for financial reasons [4].

Inequality in access to PHC is currently increasing in Belgium [5], in contrast to the overall declining trend seen throughout the rest of the European Union [6]. For example, in 2008, 1.4% of people from the lowest socio-economic quintile could not access the care they required; this proportion had increased to 8% by 2016 [7]. The organization of the Belgian PHC system is one of the main reasons for this worrying trend [10]. Over the past decades, various mechanisms have been introduced into the Belgian healthcare system to improve access to care for PECAP. Reforms include the improvement of financial accessibility through various measures to reduce co-payments [5]. Nevertheless, access to care challenges for certain groups remain—and may be becoming worse.

There is significant clustering of social groups by socio-economic position in different neighbourhoods or communities. Consequently, there is also clustering of difficulties accessing PHC in these communities, contributing to a spatial patterning of health [8]. These various forms of clustering in different communities lead to a cocktail of individual disadvantages, contextual determinants of health (e.g., poor housing conditions), and resulting health problems, all of which perpetuate each other [8]. Given the spatial relation between the overlapping vulnerabilities of socio-economic position and lack of access to PHC, a community-oriented approach is required [8]. Moreover, to improve access to care for PECAP, the current Belgium PHC model requires innovation that goes beyond the physical environment of GP practices and actively reaches out to PECAP [2, 4]. In addition, the White paper on access to care in Belgium stresses the need for a “low-threshold healthcare system,” being “a set of structures and/or services with a multidisciplinary, flexible and proactive approach, where persons with no access to normal care may receive primary healthcare” ([4]: p. 12).

Reciprocal innovation

The COMPASS research project posits that addressing access-to-care challenges for PECAP in Belgium can be achieved by drawing on innovations from low- and middle-income countries (LMICs), in accordance with the principle of reciprocal innovation. Reciprocal innovation is defined as “a bidirectional, co-constituted, and iterative exchange of ideas, resources, and innovations to address shared health challenges across diverse global settings” ([9]: p. 2). LMICs also experience challenges in ensuring access to care for PECAP, with limited resources for health and on a much larger scale than in high-income countries (HICs). Expertise, creativity, inspirational leadership, and innovative science have prompted innovation in programmes and methodology to improve access to care, even when resources are limited [10]. These out-of-the-box innovations from resource-constrained settings should inspire HICs in the quest for (cost-)effective options in the context of dwindling resources.

Recent systematic assessments of various countries’ progress towards universal access to care have designated Brazil as a top performer [11]. The country’s “Family Health Strategy” (FHS) provides a fundamental change in the healthcare delivery model, focusing on PECAP [12]. Inspired by the success of the Brazilian FHS, South Africa launched its own programme “Re-engineering Primary Health Care” [13]. Both models employ designated health teams, which comprise one physician (in Brazil only), one nurse, one nurse aide, and between four and twelve full-time community health workers (CHWs). Each team interacts with all households (up to 1000) in a geographically defined community [14]. The team is the first entry point into the healthcare system and provides a wide range of primary care services to all individuals in a household [15]. The CHWs play a central part in both countries’ innovative health models. CHWs are lay members of the socio-economically vulnerable communities who live in the area where they work and who subsequently help bridge the gap between PHC and disadvantaged communities [14]. At least once a month, irrespective of need or demand, the CHW visits each household proactively in their micro-area. CHWs focus on all members of the household with a package of health-promotion activities that fully span the life course [16]. When needed, CHWs link household members to the existing primary healthcare (PHC) system, within which the CHWs are fully embedded. CHWs therefore overcome many barriers surrounding health-seeking behavior [17].

Objectives

There is a lack of knowledge regarding the characteristics and (cost-)effectiveness of an outreach-integrated primary healthcare model that leverages the bridging role of CHWs and its integration into the primary healthcare system in Belgium [18]. The Community Health Workers for Primary Healthcare Access (COMPASS) project will address these knowledge gaps by designing, implementing, and evaluating to what extent and in what way access to PHC can be improved via a CHW intervention for people living in socio-economically vulnerable circumstances. To this end, this project aims to test if an evidence-based intervention delivered by CHWs leads to (1) increased levels of self-perceived health and (2) health-related quality of life, health literacy, patient empowerment, and reduced financial burden of health care (SPIRIT point 7).

Theoretical framework

Access to care is a longitudinal concept that starts from the perception of a health need and extends to that need being met in an appropriate manner. Levesque et al. [19] conceptualise access to care as a continuum with six steps: (i) having healthcare needs, (ii) perceiving these needs, (iii) seeking health services, (iv) reaching, (v) utilising healthcare services, and (vi) achieving the intended healthcare consequences [19]. The framework acknowledges the existence of individual and organizational barriers for each sequential step in the access-to-care continuum. PECAP often have strained capacities in accessing healthcare due to poor health literacy, language challenges, isolation, lack of trust between the provider and the patient, mobility challenges, as well as financial difficulties [4, 6]. As such, PECAP feel less able to cope with, understand, and manage their illness. These factors are interconnected and influence each other, acting at different moments along the access-to-care continuum [19]. While PECAP are often described as “hard-to-reach,” from their perspective it is the healthcare services that are hard to reach [2], such as limited consultation time, lack of care coordination, or waiting times, among others [20]. The barriers to PHC are therefore not only related to individual characteristics, but also to the organizational characteristics of PHC: “health services are not designed and organised to optimally reach and serve these groups” ([2]: p. 24).

Building on the theoretical access-to-care framework described by Levesque and colleagues [19], the conceptual model of CHW-facilitated access to primary care outlines the ways in which CHWs support people living in socio-economically vulnerable circumstances in their access to primary care [21]. Through their use of outreach methods and proactive approach to engagement, CHWs can reach people living in socio-economically vulnerable circumstances. Building trust is essential for CHWs to help underserved people living in socio-economically vulnerable circumstances in a comprehensive manner in their local community. They do so by tailoring their approach to the unique interplay between health system barriers and individual barriers experienced by people living in socio-economically vulnerable circumstances along the access-to-care continuum, as described by Levesque and colleagues [19]. Key to the CHW’s way of working is providing unbiased support and guidance in a culturally sensitive manner. It is important to note that the support provided by CHWs is also influenced by the broader health system in which they work, even while they engage with and acknowledge the access difficulties faced by PECAP. Influential factors within this system include long waiting times, a shortage of GPs, and unwelcoming healthcare professionals following a referral from a CHW [21].

Trial design (SPIRIT point 8)

The primary activity for the COMPASS study will be the implementation and assessment of the impact of a CHW intervention linked to GP practices in a cluster randomized controlled trial (cRCT) with two arms: (1) those receiving standard of care, without additional support; (2) those receiving standard of care plus the CHW intervention to improve access to PHC (SPIRIT point 6b). We opted for a randomized controlled trial (RCT) as it is the most rigorous study design for evaluating the effectiveness of interventions, allowing for causal inference by minimizing bias and confounding through random allocation. Table 1 represents a schedule of intervention implementation, assessment and dissemination. CHWs are the primary actors in this RCT: CHWs are linked to GP practices, which creates a risk of contamination if patients within the same GP practice are allocated to different trial arms. The GP practice was therefore selected as the cluster unit of randomization. The randomization process was undertaken using Excel’s random number generator. Clinics were listed in strata and given a random number. Allocation to the intervention or control arm was determined within each stratum by sorting clinics based on their random numbers, with a coin toss conducted by a senior researcher deciding beforehand whether the higher or lower numbers determined allocation to intervention or control. Blinding of the study arms was not possible because of the clear differences between the intervention and the standard of care (SPIRIT point 16c, 17a–17b).

Table 1.

Schedule of intervention implementation, assessment and dissemination

	Year 1	Year 2	Year 3	Year 4
Preparatory research activities
Ethical approval	X
Formative research in Belgium, South Africa, and Brazil	X
Quantitative survey development	X	X
Mobile data collection tool programming		X
Qualitative data collection tools development		X
Development of the CHW intervention through co-creation		X
Pilot of the COMPASS intervention		X
Drawing study sample for cRCT		X
Training “Community researchers”		X
Baseline assessment
Baseline quantitative data gathering, capturing, and cleaning		X	X
Qualitative data collection		X	X
Baseline quantitative data analysis			X
Writing of reports and articles		X	X	X
Implementing the CHW intervention
Workshops providing training to CHWs conducting the intervention		X
Eligibility screen participants		X	X
Informed consent		X	X
Implementing the intervention		X	X
Monitoring of the intervention using qualitative methods		X	X
Measuring the impact of the CHW intervention
Developing a quantitative post-intervention survey			X
Follow-up quantitative data gathering, capturing, and cleaning			X	X
Qualitative research on experience of intervention implementation			X	X
Follow-up quantitative data analysis				X
Qualitative data analysis				X
Writing of report and articles				X
Dissemination of knowledge on the CHW intervention
Presenting results at international conferences		X	X	X
Writing of report and articles			X	X
Finalizing PhDs				X

Methods/design

Study setting and site selection (SPIRIT point 9)

The cRCT will be executed in the Antwerp metropole, Belgium. In the city of Antwerp, 30.5% of the population has an increased reimbursement status, which indicates socio-economic vulnerability [22]. Antwerp is one of the ten Belgian cities where the Federal Community Health Worker (CHW) program, implemented by the National Institute for Sickness and Disability Insurance and the National InterMutualist College, is active. Federal CHWs work in an outreach capacity to support individuals living in socio-economically vulnerable circumstances in accessing care. However, the Belgian federal CHW program is not structurally integrated into the broader health system [23]. A full list of study sites, comprising the 18 participating general practices, is available upon reasonable request from the corresponding author, in order to maintain an appropriate balance between transparency and confidentiality.

Participants (SPIRIT point 10)

Inclusion criteria for participants include the following: a minimum age of 18 years; who are part of the patient registry of the participating GP practices; who were listed by the GP practice as patients who could benefit from additional support to better address a health need or health risk. This identification process required careful navigation between the methodological requirements of the trial and the practical realities of implementation. Given the complexity of the study and the multi-dimensional nature of vulnerability, developing a comprehensive checklist of what constitutes vulnerability proved impractical for GPs to use due to its excessive length. In recognition of general practitioners’ limited time and the importance of real-world applicability, we relied on their clinical judgment, acknowledging that they are best positioned to identify individuals living in vulnerable circumstances within their patient populations. Exclusion criteria will include the following: (1) individuals who will not be able to give consent for any reason, such as severe mental health disorders; and (2) individuals who already receive(d) support from CHWs as part of the Federal CHW program [24] (SPIRIT point 11d). Except for the excluded Federal CHW program (excluded because of significant possible overlap), all routine concomitant care and interventions will be permitted, contingent upon the discretion of the participant and their GP. In addition, if a patient in the control arm is extremely vulnerable, they will not be included in the study, and efforts will be made to seek appropriate support for them: this is due to the fact that it would be unethical to let extremely vulnerable individuals go without support when they have been identified.

18 GP practices were selected through convenience sampling for inclusion in the study in Arms 1 and 2—resulting in 9 GP practices or clusters per trial arm. These 18 practices (11 fee-for-service and 7 capitation practices) expressed willingness to participate, could offer logistic support during the recruitment of participants, as well as have sufficient resources (time and staff) to integrate the CHWs into their day-to-day functioning.

Sampling (SPIRIT point 14)

The primary outcome of the study is self-perceived health, measured through a 5-point Likert scale (excellent, very good, good, fair, and poor). In prior research, self-perceived health has commonly been dichotomized into two categories: “good” health (including excellent, very good, and good) and “poor” health (including fair and poor). A 10% absolute increase in the prevalence of participants reporting “good” health has been previously defined as a clinically relevant change [25].

Based on the Belgian Health Interview Survey, 77% of the general population in Belgium reported “good” health [25]. However, given that the study targets a subpopulation characterized by multifaceted vulnerability, we assumed a baseline prevalence of 50% reporting their health as “good.” While the benchmark for clinical relevance is a 10% increase, for sample size estimation we hypothesized a larger effect (an absolute increase from 50 to 80%), reflecting the expected potential of a targeted intervention in a highly vulnerable group. We acknowledge that this assumption is more ambitious than the clinically minimal relevant difference, and we clarify it here to avoid confusion between the two values.

Given that this is a cluster randomized controlled trial at the GP practice level, the sample size estimation accounted for the design effect due to clustering, applying a conservative coefficient of variation of 0.25. The sample size was subsequently estimated with 80% power and a 95% significance level, using Stata 17. Assuming a cluster size of 17 participants per cluster, 8 clusters per arm are required to detect the hypothesized effect. Adding one additional cluster per arm due to stratification results in 9 clusters per arm, or 18 clusters in total. To account for an anticipated dropout rate of 20%, a final sample size of 21 participants per cluster is required, equating to 378 participants overall, or 189 participants per arm.

Recruitment (SPIRIT point 15)

After the participating general practitioner (GP) teams have identified patients in need of additional support, these patients will receive a letter informing them about the study (see Fig. 1). Subsequently, trained community researchers will contact the patients via telephone to schedule an initial visit at a location of the respondent’s preference, such as their home or the GP practice, for further explanation of the research project. Community researchers are people with shared lived experience as the participants in the trial, i.e., people living in socio-economically vulnerable circumstances. Community researchers received training in research-related tasks prior to commencing as volunteers on the cRCT (receiving a stipend). During the first visit, the community researcher provides further information about the study. There is room for questions, and if the patient expresses willingness to join the cRCT, they are invited to sign the consent forms. The recruitment process is undertaken concurrently at control and intervention sites. If the patient refuses to participate, the patient stays in the regular Belgian health system, and no further contact from the study team is made. If the participant agrees to be included in the study and signs the consent form, the community researcher enrols the individual and conducts the baseline survey. In the intervention arm, the community researcher schedules a first visit with the CHW. Because of anticipated challenges in reaching and staying in contact with the respondent, it is important that the first visit with the CHW is organized as soon as possible and that introductions are made: it is not therefore possible to blind researchers or patients as to the arm of the intervention they are in, as the community researchers have to explain the full research flow to the participant and subsequently introduce the CHW to the participant in the intervention arm. We acknowledge that this lack of allocation concealment may introduce selection bias. However, this approach was adopted following careful deliberation, balancing methodological rigor with the practical requirements of implementing the intervention. The decision reflects the necessity for community researchers to transparently explain the intervention process, including the role of the CHW, to participants in the intervention arm (SPIRIT Point 16a-c).

Fig. 1.

Schedule of enrolment, interventions, and assessments

Intervention (SPIRIT point 11a)

The PHC models in Brazil and South Africa [12, 13] were adapted to the Belgian setting through a co-creation process guided by the ADAPT framework [26]. In addition, the intervention development process was guided by the “Six steps in Quality Intervention Development” (6SQuID) model [27]. The 6SQuID model has repeatedly proven to be successful in the development of health-behavior interventions, including during previous projects undertaken by the research team [28]. The integration of both frameworks and the development of the intervention will be described in detail elsewhere [29].

Piloting the COMPASS intervention

The intervention pilot was executed over the course of one and a half months (September–October 2024) with a small sub-sample of three patients from a GP practice that was not subsequently included in the cRCT. All patients provided written informed consent to participate in the pilot study. Two patients in the control arm and one patient in the intervention arm conducted the survey—administered by a PhD student who trains and supervises the community researchers. In addition, the patient in the intervention arm received support from a CHW. During the pilot, the role of the CHW was fulfilled by the CHW-supervisor.

The COMPASS intervention

Participants in the intervention arm receive standard care plus a CHW-led intervention, while the control arm only receives standard care. Standard care for PECAP in the larger city of Antwerp involves patients making their own appointments with their GP and/or accessing care or social support via their own initiative.

In the intervention arm, 6 part-time (80% FTE) CHWs are employed in the 9 intervention GP practices to perform the intervention visits for the sampled patients (21 patients per GP practice) over the course of 12 months. The CHWs participating in this trial were selected through an application process based on various criteria, including being familiar with vulnerable neighbourhoods in the Antwerp metropole; knowledge of local language(s); strong communication skills; having knowledge and understanding of problems people may have with health care (from interest and/or personal experience); confidence and skills in dealing with difficult and/or emotional conversations and situations; ability to handle sensitive information confidentially and discreetly; ability to organize their own workload and work without direct supervision, among others. No formal educational qualifications or specific training requirements were stipulated during the recruitment process. At the time of recruitment, all CHWs resided in Antwerp, a city marked by considerable demographic diversity. It was, of course, not feasible to recruit six CHWs who each individually reflected the full spectrum of this diverse study context (especially given that over 100 languages are spoken in Antwerp). Consequently, we assembled a team that is both diverse and coherent, enabling members to complement one another and provide mutual support as needed.

Participants in the intervention arm receive CHW support over the course of 12 months. Through monthly home visits or phone calls to check in on progress, the CHW builds trust with their individual client and gains insight into their client’s health situation, their personal goals around health, and the barriers they experience in achieving them (cfr. Table 2). The CHW subsequently addresses these barriers as far as they can, to the extent to which they are able to do so, enabling participants to gain more control over their health in the long term. During each intervention visit, the respondents are encouraged to invite and, where possible, bring other household members to the next visit. Inviting a household member to participate is not, however, a prerequisite to continue in the study. A structured intervention manual has been developed, offering a comprehensive overview of each component of the intervention. Upon completion of the study, the manual will be made publicly accessible via the research study website.

Table 2.

Brief overview of the COMPASS intervention

Step	Content		Supporting documents and tools
Step 1	During the first introductory visit the CHW and client get to know each other (first month)		• To support project introduction, an informational document may be provided to clients, summarizing key details and including contact information. A section for mutual agreements allows documentation of preferred communication methods and availability, with copies retained by both CHW and client • An appointment card facilitates scheduling by noting the date and location of the next meeting, aiding client recall • In cases of missed home visits, a “Sorry I missed you” card can be left to inform the client of the attempted visit and provide contact details
Step 2	The CHW will deliver the core components of the intervention over the course of the next 10 months. In this second step, five blocks are identified that the CHW will focus on—at the pace of the client:		• To support continuity and reflection during home visits, CHWs may complete the “Our COMPASS” document together with the client across multiple sessions. This tool enables tracking of previously discussed topics and facilitates ongoing dialogue • Additionally, CHWs are asked to update the Excel sheet after each client contact. This ensures a structured overview of all interactions throughout the intervention period
	Block 1	Household assessment	• The household assessment consists of a structured list of questions aimed at gaining insight into the family context and key health needs, while avoiding overwhelming the client. It may be completed gradually over multiple visits. This tool supports the CHW in developing a clear and comprehensive understanding of the client and household situation
	Block 2	Personal goal setting and action plan	• To initiate dialogue around what matters in a person’s life, CHWs may use the illustrated page “What Matters in One’s Life” as inspiration during the first step of the intervention. This visual tool presents a range of themes that individuals may consider important, including family and friends, pets, food and drink, finances, health, hobbies, household tasks, nature, education, travel, religion, social contact, sports, transportation, appearance, and work
	Block 3	Helping the client to become acquainted with the healthcare landscape	• Existing work conducted by CHWs during the community mapping exercise may be used to support referrals. Preferably, clients are directed to local organizations • The referral platform Zipster can also assist in identifying appropriate services
	Block 4	Social integration with a focus on both professional and informal network/links	The intervention follows two complementary pathways • First, clients are connected to social organizations active in the neighborhood, using resources such as Zipster, the social map, and insights gathered during the community mapping process • Second, efforts are made to engage and strengthen the client’s informal support network. In this context, CHWs have the flexibility to initiate activities that align with the client’s needs and are adapted to the specific characteristics of the local community
	Block 5	Engaging in prevention and mental health	• A thematic calendar is provided, outlining monthly topics related to prevention and health promotion. At the beginning of each month, a trainer provides an overview of the prevention topic and introduces the corresponding materials. Time may be allocated during team meetings or training sessions for this purpose. The focus and selection of materials are determined in consultation with the CHW-coach
Step 3	In the last visit—in the twelfth month—the CHW carries out a concluding session with the client to plan in which way the client will take care of his or her own health in the future		• The “Our COMPASS” document may be revisited together with the client to reflect on progress and reassess needs • If further support is required, clients can be referred to the CHWs in Antwerp. To facilitate this referral, the “CHWs Flyer” may be provided to the client

Implementation of the COMPASS intervention

A six-week training programme was held for the CHWs in the intervention arm of the cRCT. The goals of the training programme were threefold: to ensure the CHWs had the relevant knowledge and skills; to inform CHWs about their specific tasks; and to ensure that the CHWs were well versed in the intervention materials. The training included key concepts such as the social determinants of health, health literacy and community health work, as well as effective communication and client management skills. The training also covered the health care system in Belgium and the legal framework within which they work. In addition, the training aimed to: develop CHWs’ confidence in working with clients by practicing scenarios; explore and understand different cultural attitudes towards health and working in a diverse cultural context; and facilitate CHWs in exploring their own values and attitudes towards their work, as well as their understanding of how to deal with their own values and attitudes while working with clients (SPIRIT point 11c). Subsequent to the training, the CHWs deepened their knowledge of the neighbourhood of their assigned GP by conducting community mapping, focusing on the support organizations based in the neighbourhood.

The CHWs in the intervention arm receive supervision from a part-time supervisor (50% FTE), who organises weekly debriefing sessions with the CHWs to assess how the intervention visits are going, to provide guidance on how to address individual cases, to monitor compliance with the intended standard of the intervention delivery, and to improve adherence to the intervention protocols.

Various strategies are followed to maximize participant retention in the study (SPIRIT point 18b). Firstly, the community researchers and CHWs send regular messages to the patients to remind them about an upcoming appointment. Secondly, the visits from the community researcher or CHW are scheduled as flexibly as possible and at the participants’ convenience.

Participant timeline (SPIRIT point 13)

Figure 1 shows details on the schedule of enrolment, intervention, and assessment.

Outcomes (SPIRIT point 12)

To assess the impact of the intervention, primary and secondary outcomes are measured at baseline, at follow-up at 6 months (selection of secondary outcomes), and at endline at 12 months. The primary outcomes for this study are self-rated health (SRH), as measured by the first question of the Short Form 12 Health Survey: “How do you rate your own health on a five-point Likert scale [30]?” The primary outcome will be categorized and aggregated as a proportion. SRH is a valid, prognostic, patient-centered, and sensitive indicator of overall health that complements objective biomedical measures [31–33]. SRH integrates information across physical, mental, and social health domains that may not be fully captured by disease-specific clinical endpoints.

With the endgoal of COMPASS being to improve the health of PECAP, this outcome was therefore deemed to be an important primary outcome. The secondary outcomes—measuring Health Literacy (HLS-EU-Q6) [34], empowerment (Client Empowerment in Community Health Systems Scale) [35], and financial burden of health care (Health Interview Survey, Sciensano) [36]—were chosen based on existing CHW literature as well as on findings during intervention development. Health care use (Medical Consumption Questionnaire (iMCQ) [37]) and Health-related Quality of Life (EQ-5D-5L [38]) were included to enable the economic evaluation.

Data collection (SPIRIT point 18a)

The COMPASS research project aims to analyse unique longitudinal data in a partially mixed concurrent equal status design, which involves “conducting a study that has two phases that occur concurrently, so that the quantitative and qualitative phases have approximately equal weight” ([39]: p.268). Quantitative and qualitative longitudinal methods are both used to capitalize on the strengths of each approach. This methodological triangulation produces a more comprehensive picture of the impact of the COMPASS intervention. The quantitative and qualitative data collection will occur simultaneously but will be analysed separately. The research team meets regularly to discuss both methods and analyses, in order to inform the development of the other. The findings of both research methods are integrated in the concluding phase of the study.

Recruitment of participants started in November 2024. Baseline data is collected during the recruitment of participants. Follow-up data will be collected 6 months and 12 months after enrolment.

Quantitative data collection

After obtaining written informed consent, the quantitative data collection is performed by community researchers who will administer the questionnaire on a hand-held device, using Qualtrics software with each respondent face-to-face. Data monitoring is ensured through both extensive training and ongoing oversight of data collectors and data collection tools. All data collectors received detailed training on standardized administration of the questionnaires, followed by regular supervision to maintain consistency. During data collection, a researcher conducted weekly reviews of a random sample of records to check for completeness and accuracy. In addition, the electronic data capture system included automated range and consistency checks. These rules prevented out-of-range or illogical responses at the point of entry, thereby improving data quality.

Information will be collected on the primary and secondary outcomes, as well as on socio-demographics, health status, socio-economic status, and healthcare resource use. The outcome evaluation for this study will be based on data collected both at baseline and during the follow-up survey. Items from the Belgian national health survey, administered by Sciensano (Belgian public health institution) [25], were adapted for the survey. Furthermore, items measuring access to care as conceptualized by the Levesque framework were adapted from items gathered by [40]. Health care consumption was measured using the validated medical consumption questionnaire [37], whereas health literacy was measured using the HLS-EU-Q6 [34]. The EQ-5D-5L measures health-related quality of life and is validated for use in Belgium [38]. The primary outcome, self-rated health, is the first question of the validated SF-12 [41]. Empowerment was measured by the Client Empowerment in Community Health Systems Scale: Development and validation in three countries [35]; although it is validated in three countries, it is not yet validated for use in Belgium. Items regarding income and financial hardship were adapted from two previous studies [42, 43]. To measure delayed healthcare usage, items from the Antwerp health survey were adapted [22].

Baseline data collection

After obtaining written informed consent, baseline data will be collected in both arms before the start of the intervention to determine the baseline levels of selected health outcomes.

Follow-up data collection

During follow-up at 6 months, a shortened questionnaire will be conducted, comprising the primary outcome, healthcare use (iMCQ) [37], and health-related quality of life (EQ-5D-5L) [38]. In order to ensure maximum comparability, the 12-month follow-up survey collects information on the same outcomes as the baseline questionnaire from the same respondents in both the intervention and control arms of the cRCT (i.e., the primary and secondary outcomes; socio-demographics; and socio-economic status; costs; healthcare resource use; healthcare needs; and healthcare usage). The following data will additionally be collected in the intervention arm after the last intervention visit at month 12: visited GP after referral of the CHW; linkage to social activities; appropriateness of referrals; among others. The same data gathering procedure as is applied in the baseline data collection will be followed for the follow-up assessment.

Qualitative data collection

During the implementation of the intervention, qualitative data will be collected through several methods: a structured diary maintained by each CHW; a reflective diary kept by the CHW-supervisor; non-participant observations of two working days for each CHW involved in the intervention; and multi-disciplinary team meetings at the GP practices in the intervention arm. In addition, in-depth interviews will be conducted with three respondent groups: (1) the CHWs; (2) recipients of the CHW support; and (3) the members of the GP practices in the intervention arm. These three groups of respondents will be interviewed at two time points: at 6 months and at the end of the intervention. Additionally, the members of GP practices are interviewed at the start of the intervention and will receive monthly check-in moments. The aim is fourfold: to assess (1) the acceptability and feasibility of the intervention; (2) the interrelationships between the actors involved; (3) the unintended consequences of the intervention (positive and negative); and (4) the context in which the intervention is implemented to understand why the intervention has or has not been successful.

Data processing and management (SPIRIT point 19)

All quantitative data will be anonymized, and qualitative data will be pseudonymized and stored on the personal University of Antwerp server of the research team, which is only personally accessible through logging in on the secured intranet of the University. In addition, logging in on the personal computer is also required, which is protected with a different password and account. Hence, the files on these personal disks are secured by the Internet and Communication Technology services of the University of Antwerp. The server of the University of Antwerp has sufficient capacity to store the estimated amount of data for this research project. After the research project, the data will be stored for 5 years beyond the end of the project in an appropriate data repository.

Quantitative data processing and management

The Qualtrics platform is used to collect and manage the quantitative data. The incoming survey data—collected through the Qualtrics platform—is already pseudonymized. The data is only available to those who are authorized, since the computer system that will be used to store it will be password protected. At the start of the trial, each patient is given a unique identification number, which will be used to gather data over the follow-up periods. The International Conference on Harmonisation Guidelines for Good Clinical Practices [33] will be followed in the management of data. An external hard drive with a password will be used for data backups.

Qualitative data processing and management

After written informed consent is obtained, all interviews will be audiotaped, allowing a detailed transcript of the interviews to be produced. After uploading the audio recording on a secure server, the recording will be deleted from the recording device. These recordings will be transcribed to ensure the accuracy of what is said and serve as the basis for data analysis. The recordings of the interviews will be transcribed verbatim. If any statements would potentially reveal the identity of a respondent (e.g., because the respondent gives information specific to a certain household or patient), the research team will further pseudonymise their transcript to protect their identity. Transcripts will be imported into NVivo. Each respondent will be given a unique identifier. The coding sheet with all respondent numbers (identifiers) will be stored on a secure campus server. The audience will not, therefore, be able to link individual statements to interviewees (SPIRIT point 27).

Data analyses (SPIRIT point 20a–20b)

Quantitative data analysis

Stata/R/SPSS software will be used for data analysis. A statistical analysis plan has been developed to guide analysis. Please see Appendix 3 for further details. Continuous data will be summarized with the mean, standard deviation, median, minimum, and maximum; categorical data will be summarized by counts and percentages. The primary aim is to assess the net impact of the CHW intervention on the access-to-care continuum by comparing outcomes in different trial arms. Standard statistical methods for conducting analysis assume that observations from individual participants are independent; however, a key feature of a cluster-RCT is that observations on participants within the same cluster are likely to be correlated and variation is observed between clusters. All analysis will therefore employ techniques specific to cluster-RCTs to account for clustering by, for example, using cluster-level analysis and generalized linear mixed models. Baseline data will be analysed to characterise the study population and assess any imbalances at baseline. End line analysis will employ a standard intent-to-treat (ITT) approach and will incorporate analysis of health outcomes as well as dose-response. The comparison between the two arms using cluster-specific analysis techniques will allow us to assess the net impact of the COMPASS intervention on both the primary and secondary outcomes. Subsequent to the intent-to-treat analysis, we will perform an analysis based on dose-response data. Dose-response analysis will examine the relationship between the primary and secondary outcomes and the following: (a) binary “minimum adherence” (≥ X visits), (b) total number of visits and points of contact, (c) intensity-weighted dose (in-person vs phone contacts). The minimum dose for “exposure to the intervention” is having completed the activities “household assessment” (block 1) and “setting health goals” (block 2). Further doses are considered to be exposure to further contact with the CHW, whether in-person or by phone. Sensitivity analysis will be conducted to consider the minimum dose to consist of one “in-person” visit.

If a patient drops out, the research team will try to trace the respondent to understand the reason for this loss to follow-up. Reasons for drop-out will be collated in a CONSORT flowchart (SPIRIT point 18b). To monitor the attrition between the first and second wave, an attrition analysis will be conducted. Missing outcome data in the intention to treat analyses will be handled with multiple imputation. Please see the data analysis plan for further details in the Appendices (SPIRIT point 20c).

Economic evaluation

An economic evaluation based on the data of the cRCT will be conducted to assess the cost-effectiveness of the intervention in addition to usual care, compared to usual care alone. The primary outcome of the cost-effectiveness analysis will be the ratio of the incremental costs to the incremental health effects (expressed as quality-adjusted life years (QALYs)), called the incremental cost-effectiveness ratio. A healthcare sector perspective will be applied, meaning the direct medical costs to the health insurer and to the patient will be accounted for. In the intervention arm, the costs associated with the intervention will also be accounted for. Discounting of future costs and QALYs is not required since a time horizon of 1 year is considered. One-way sensitivity and probabilistic sensitivity analyses will be performed to address uncertainties related to the values of key input parameters.

Qualitative data analysis

Data collection and data analysis phases will be alternated to assist subsequent interviews and to assess when data saturation has been reached. Data will be analysed carefully by reading and re-reading the field notes and transcripts of interviews. Codes for a sample of transcripts will be compared with another researcher’s codes, and similarities and differences will be discussed. The analysis will be performed in accordance with the thematic analysis procedures by Braun and Clarke [44].

Monitoring

When baseline data becomes available, descriptive analysis will be conducted (SPIRIT point 21b). A dedicated Trial Steering Committee (TSC), composed of representatives from both participating universities, will be responsible for overseeing the progress of the trial and ensuring compliance with the established protocol. In addition to monitoring trial conduct, the TSC will safeguard participant safety, uphold ethical standards, and provide expert guidance on matters of scientific integrity and feasibility. The committee will convene on a biweekly basis and will include a diverse membership comprising junior and senior researchers as well as professors. Importantly, the TSC will operate independently of the funding body. Furthermore, the study is guided by a Scientific Advisory board, consisting of international scientific experts, and a Societal Advisory board, consisting of representatives of organizations working with socio-economically vulnerable groups; (organizations representing) primary healthcare providers; representatives of healthcare projects for socio-economically vulnerable groups; and policymakers in Belgium. Both advisory boards convene on an annual basis to evaluate the progress of the study, offer feedback on proposed next steps, and ensure that the research remains aligned with community priorities and the broader international scientific literature (SPIRIT point 5d, 21a, and 23).

Adverse events resulting from the intervention are reported on the same day to the principal investigator (PI), who will report these to the ethics committee of both institutions involved in the study (i.e., University of Antwerp and University of Ghent). In case of a particular adverse event, the PI will make an informed decision whether to continue the trial for this participant. The PI, who has decades of research experience, will be responsible for assessing each reported adverse event. This includes evaluating seriousness, severity, and potential causality based on the following criteria: Related: there is a reasonable possibility that the study intervention contributed to the adverse event; Unrelated: there is no suspicion that there is a relationship between the study intervention and the adverse event (e.g., natural history of underlying diseases, concomitant therapies). This assessment will be informed by participant reports, CHW observations, and, where relevant, consultation with healthcare professionals. All adverse event assessments and decisions will be documented and, if necessary, discussed with the ethics committees of the University of Antwerp and the University of Ghent. If an individual participant does not want to continue participation in the study, their participation in the intervention will be stopped. If the respondent consents, the follow-up survey will be conducted at that moment. Participation (intervention exposure) will be accounted for in the analysis by including the number of concluded CHW visits (SPIRIT point 11b). In the event that psychological support is needed, the research team will provide counselling contacts (SPIRIT point 22). In the unlikely event that the intervention has a negative effect on the health or mental well-being of the participants, the project partners—University of Antwerp and University of Ghent—must mutually decide in consultation with one another and the ethics committees of both institutions whether or not to continue the cRCT (SPIRIT point 21a and 21b).

Ethics, consent and permissions

Permission to carry out the study was obtained from the Social Ethics Committee for the Social Sciences and Humanities, under file code SHW_2023_98_1. An addendum was submitted and approved (SHW_2024_126) with specifics regarding the cRCT. Written informed consent will be obtained from all study participants by the community researcher, and the confidentiality of the study participants will be maintained throughout all stages of the study (SPIRIT point 26a). The consent forms are available in Dutch and English. The purpose of the study, its design, and aspects such as informed consent and confidentiality are explained in a manner comprehensible to the respondent. This information is also distributed by means of an information leaflet, which the participants receive from the community researcher. Written informed consent is required not only for study enrolment but also for audio recording and for the publication of the findings. After written informed consent, respondents who have agreed to be included in the study either undergo (1) a baseline and follow-up survey or (2) a baseline and follow-up survey plus a CHW intervention.

Respondents can withdraw from the study at any time without penalty or loss of benefits to which they are entitled. If the respondent does not want to discuss certain (sensitive) issues, the researcher will be sensitive to the limits of the participants, not pressing the issue and going on to the next question.

Ancillary and post-trial care (SPIRIT point 30)

There are three groups involved in the COMPASS study: (1) individuals living in socio-economically vulnerable circumstances receiving the CHW intervention; (2) CHWs providing the intervention; and (3) team members of the GP practices. Group 3 is not exposed to any risks. These participants will share their views and experiences as part of the qualitative acceptability and feasibility study regarding their work and involvement in the intervention.

CHWs (group 2) face certain risks due to the complex cases they may encounter in their work. To address this, weekly supervision sessions with the CHW-supervisor are organized to discuss these cases and provide support to the CHWs. If necessary, additional psychological support will be sought for the CHWs.

Participation in this study might cause stress or anxiety (psychological disadvantages) for individuals living in socio-economically vulnerable circumstances (group 1) as questions will focus on the difficulties that they experience in accessing PHC. Explicitly addressing these topics might emphasize a painful or stressful situation. Interviewers will be trained and will be attentive to the emotional state and boundaries of participants. The informed consent form clearly mentions the possibility of skipping questions or withdrawing from the interview at any time without consequences. These options will also be stressed by the interviewer.

Participants living in socio-economically vulnerable circumstances in the intervention arm will be subjected to the COMPASS intervention. The intervention is based on the available literature on intervention development and the existing CHW intervention in FHS in Brazil and Re-engineering PHC in South Africa [12, 13]. The entire intervention development process also incorporated all relevant stakeholders through a co-creation process, namely people living in socio-economically vulnerable circumstances, CHWs, and GPs. However, it must be noted that every intervention can have unintended (negative) consequences. When the CHWs deem it necessary, they will also further refer to relevant health or social development government services or community-based or non-governmental organizations. In the unlikely event that a participant experiences harm directly related to the study, the research team will ensure that appropriate medical, psychological, or social support is provided.

To ensure ethical and effective closure of the intervention, particular attention will be paid to avoiding an abrupt conclusion, especially given the vulnerable nature of the study population and the trusted relationships developed with CHWs. Participants will be informed in advance about the end of the trial, and CHWs will be instructed to facilitate a gradual transition, as outlined in the intervention protocol (see Step 3). In this final step, clients are invited to reflect on the goals established during the intervention, considering strategies to continue pursuing these objectives and organizing their access to healthcare independently. This phase also includes a joint reflection on the client’s overall experience with the intervention. As CHW support concludes after 1 year, the overarching aim is to empower clients to sustain independent and equitable access to appropriate healthcare services, supported by their social networks and with continued attention to preventive care. In the context of program scale-up, it is anticipated that CHW involvement would similarly be limited to approximately 1 year, with the intervention structured to promote long-term self-reliance and integration into existing community and healthcare systems. If additional support is required at the conclusion of the intervention, the COMPASS team will undertake efforts to facilitate the linkage of participants to appropriate community-based or primary care support services. This transition will be tailored to individual needs, recognizing that each participant may require different types and levels of support after the study concludes. A comprehensive but accessible access-to-care guide will be developed by the COMPASS team and shared with participants in both arms of the cRCT.

Dissemination of results and findings (SPIRIT point 31a)

The study results will be presented to the scientific community via journal publications and presentations at international conferences. People who are formally named and linked to the study and others who are directly involved, who have actively participated in the preparation or writing of the articles, are eligible for authorship. There is no intention to make use of professional writers (SPIRIT point 31b). Furthermore, all relevant stakeholders will be informed of the research results through the yearly Scientific and Societal Advisory Board. In addition, through short policy briefs, policymakers will be informed about more elaborate policy advice. Moreover, communication materials will be developed to ensure that the research results are communicated in an easy-to-understand way to people living in socio-economically vulnerable circumstances (e.g., a poster with an infographic of the research results).

Discussion

Even though various mechanisms have been implemented in the Belgian healthcare system to improve access to care, inequality in PHC access has been increasing in the past decade [7]—creating the need for innovative measures. A new health care model should therefore be designed and tested to link PECAP to the existing PHC system. Since the country is also confronted with increasing health demands and limited budgets, there is impetus to tap into the potential of innovations from LIMCs—in a reciprocal manner. A review of health innovations in LIMCs and a theoretical analysis on the required characteristics of such a new model resulted in a CHW intervention—inspired by the Family Health System in Brazil and Re-engineering PHC in South Africa [12, 13]. We hypothesise that a PHC model with a CHW intervention employing outreach methods will address the access-to-care challenges in Flanders, Belgium. This paper provides an overview of the COMPASS-cluster RCT, in which a CHW intervention linked to the PHC system will be implemented and evaluated. As such, our study will contribute to the much-needed body of knowledge on the (cost-)effectiveness of employing CHWs in primary healthcare in Belgium.

The COMPASS study has encountered various challenges to date: (1) recruitment of GP practices proved to be challenging given that all GPs in the region of Antwerp stated that they had very high workloads; (2) the definition of inclusion criteria has changed based on the lessons learned in the pilot; (3) the selection of the primary outcome was challenging as internationally validated scales were usually not adapted to the target population of this study, i.e., people living in socio-economically vulnerable circumstances; (4) the CHWs had to be recruited before the GP practices were randomized, meaning that CHWs could not be specifically recruited from the communities immediately surrounding the GP practice; and (5) the way in which we can make the COMPASS study genuinely reciprocal by exchanging lessons learned between LMICs and HICs participating in the study.

Trial status

The Ethics Committee for the Social Sciences and Humanities, under file code SHW_2023_98_1 and SHW_2024_126, provided ethical approval for this study on the 19th of June 2024. Recruitment of study participants commenced on November 28th, 2024, and was completed by June 11th, 2025. Baseline data are being collected after participant recruitment, and the final data collection will be completed by May 2026.

Abbreviations

CHW

Community health worker

COMPASS

Community Health Workers for Primary Health Care Access

EQ-5D-5L

EuroQol-5 Dimensions-5 Levels

FHS

Family Health Strategy

GP

General Practitioner

HLS-EU-Q6

European Health Literacy Survey Wuestionnaire—6 Dimensions

HICs

High-income countries

HRQoL

Health-related quality of life

iMCQ

Medical Consumption Questionnaire

ITT

Intent-to-treat analysis

LMICs

Low- and middle-income countries

PECAP

People who experience challenges accessing primary healthcare

PHC

Primary Health Care

Cluster-RCT

Cluster-randomized controlled trial

SPIRIT

Standard Protocol Items Recommendations for Interventional Trials

6SQuiD

Six steps in Quality Intervention Development

Authors’ contributions

CM: Assistant professor and post-doctoral researcher; wrote the funding proposal together with EW, HB, JvO, NV; key in designing the CHW intervention; overall management of RCT implementation; co-facilitator of the CHW training; contributed to the quantitative and qualitative data collection tools; participation in quantitative and qualitative data analysis; key author of this current article. EoB: PhD student; training and managing community researchers; managing quantitative data collection; key in designing the CHW intervention; liaison with GP practices; co-facilitator of the CHW training; key in the collection of qualitative data; participation in quantitative and qualitative data analysis; contributed to this current article. TvI: PhD student; key to survey instrument design and Qualtrics programming; liaison with GP practices; co-facilitator of the CHW training; key in designing the CHW intervention; participation in quantitative, health economic, and qualitative data analysis; contributed to this current article. LV: PhD student; key in conducting fieldwork in South Africa and Brazil; key in designing the CHW intervention; co-facilitator of the CHW training; key in the collection of qualitative data; participation in quantitative and qualitative data analysis; contributed to this current article. LC: PhD student; key in designing the CHW intervention; key in designing the survey instrument; developed the CHW training and the corresponding training manual; co-facilitator of the training; oversight of all data management and processing; major participation in quantitative data analysis; contributed to this current article. NvH: Professor; wrote the funding proposal together with CM, EW, HB, JvO; contributed to survey instrument design; supervision of the health economic data collection and analysis; contributed to this current article. JvO: Associate Research Professor; wrote the funding proposal together with CM, EW, HB, NV; contributed to survey instrument design; participated in quantitative and qualitative data analysis; contributed to this current article. HB: Full professor; wrote the funding proposal together with CM, EW, JvO, and NV; key input in qualitative data collection tools; leads qualitative analysis; contributed to this current article. EW: Full professor, PI; wrote the funding proposal together with CM, HB, JvO, and NV; key input in quantitative data collection tools; oversight of all data management and processing; leads quantitative analysis; contributed to this current article. All authors read and approved the final version of the manuscript.

Funding

Fonds Wetenschappelijk Onderzoek,S006123N.

Data availability (SPIRIT Point 29)

The access to the dataset is currently restricted to the project research team members of two research institutions (University of Antwerp and University of Ghent). The same applies to the statistical code (SPIRIT point 31c). In due course, these may be made available by the UA PI (EW) on reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval was granted by the Ethics Committee for the Social Sciences and Humanities (SPIRIT Point 24). If further protocol amendments are required, they will be sent to ethics committees for review and approval (SPIRIT point 25).

In addition, a legal contract between the University of Antwerp and the University of Ghent has been signed.

Consent for publication (SPIRIT point 26a)

Informed written consent will be required from all participants before enrolment in the study (cfr. Appendix 2, SPIRIT point 32).

Competing interests (SPIRIT point 28)

The authors declare that they have no competing interests.