Background and rationale

Non-medical health related social problems are highly prevalent in primary care [1]. They can significantly influence the incidence of mental and somatic conditions [2–4], but can also be caused by (chronic) diseases. They are associated with relevant economic costs, such as sick leave and long-term absence from work [5–7]. Non-medical health related social problems are operationalized through the International Classification in Primary Care 3nd Edition (ICPC-3) in chapter ZC “Social Problems” [8] and include problems such as loneliness, problems in the family and at work, as well as financial difficulties [1,9]. These problems disproportionally affect people with a lower socioeconomic status and increase health inequalities [10].

Although non-medical health related social problems are common in general practice, General Practitioners (GPs) can target only a few problems during their consultations [11]. Although there is an extensive range of non-clinical support and services available in the communities in Germany, there are no formalized connections between these services and primary care [12]. Thus, it is difficult for both GPs and patients to choose the right point of entry when problems arise. This calls for low threshold, cooperative solutions [1].

Several potential solutions have been suggested, including integrated primary care centres, provision of social work in primary care, and social prescribing (SP) [13]. SP equips GPs with a non-medical referral option, which can accompany existing treatments to improve health and well-being [14]. SP was developed in the United Kingdom and has become widely established in the National Health Service in recent years. Globally, SP schemes have been implemented in several countries such as Canada and Singapore, but also Austria and the Netherlands [15]. In a recent survey we could show that there is a high interest in Social Prescribing among German GPs [13,16].

From the existing evidence, the need for randomized controlled trials to assess the efficacy of SP - especially outside of the United Kingdom, is evident [17]. However, as there is limited experience with establishing SP in Germany, a feasibility study is a necessary first step to clarify aspects for a future randomized trial. Important aspects are the acceptability of the trial by potential participants, loss to follow-up, the number of appointments between patients and link workers needed, the feasibility of endpoint measurements as well as the acceptance of the link worker role in the German health care system. This evidence is essential before implementing Social Prescribing into routine care in Germany [18].

Objectives

The goal of this trial is to test the feasibility of a randomized controlled trial and potential benefit of SP in the primary care setting in Germany.

Trial design

The trial is designed as a multi-center, two-armed open, exploratory, individually randomized controlled, pragmatic, feasibility trial. The study procedures follow the guideline for good clinical practice E6 (R2). The study protocol used the SPIRIT reporting guidelines [19]. A SPRIT schedule can be found in Fig 1. An overview of the study design can be found in Fig 2.

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Fig 1. SPIRIT schedule of enrolment, interventions and assessments for the trial.

https://doi.org/10.1371/journal.pone.0322372.g001

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Fig 2. Design of the feasibility trial.

https://doi.org/10.1371/journal.pone.0322372.g002

SP is compared with treatment-as-usual plus a brochure with information about local offers for non-clinical support and services in the community (TAU+). We decided on a multi-center approach to reach the necessary sample size and allow the results to be more generalizable. This also allows for more flexibility in the delivery of the intervention, which will be analyzed in the process evaluation. In this feasibility trial, study centers are GP practices in Berlin and Brandenburg.

We decided to perform individual randomization in a 2:1 allocation ratio (intervention:control). A randomized design was chosen to assess the feasibility of individual randomization in the primary care setting. We decided for a 2:1 allocation ratio to ensure that enough participants are in the intervention arm for the main feasibility endpoints. A control group is needed to provide information on the feasibility of the proposed control group design and trial processes especially regarding loss to follow-up in the control group. Cross-contamination will be analyzed in the qualitative process evaluation to assess the feasibility of individual randomization compared to cluster randomization. A highly pragmatic approach was chosen because the intention of the future confirmatory trial will be to inform real world clinical choices of implementing SP into routine primary care [20,21]. Fig 3 shows the expected patient flow following the CONSORT flow diagram.

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Fig 3. Expected participant flow.

https://doi.org/10.1371/journal.pone.0322372.g003

Study setting

The trial is conducted in the primary care setting. Study centers are nine GP practices in Berlin and Brandenburg. After recruitment in the GP practice and issuing of a social prescription, the Link worker sees the patients preferably in the GP practice, alternatively as a home visit or by telephone. The study centers are the following:

Dr. med. Kathrin Hecker

Landsberger Allee 44

10249 Berlin

Study site initiated 25.10.2024

Ärzte am Hermannplatz

Gerd Michels

Kottbusser Damm 72

10967 Berlin

Study site initiated 12.09.2024

MVZ Praxis Korok

Rheinsteinstr. 1

10318 Berlin

Study site initiated 18.09.2024

Hausarztpraxis Lichtenberg

Iris Boehmer

Möllendorffstr. 45

10367 Berlin

Study site initiated 19.09.2024

Gesundheitszentrum Haus Nazareth

Dr. med. Burghard Storm

Wrangelstr. 6/7

12165 Berlin

Study site initiated 04.11.2024

Hausarztpraxis Dashti

Dr. med. Hiwa Dashti

Am Paschenberg 30

16225 Eberswalde

Study site initiated 09.09.2024

Hausarzt Dr. Zerbaum & Kollegen MVZ

Dr. med. Mario Zerbaum

Petersilienstraße 12

14776 Brandenburg

Study site initiated 16.09.2024

Hausarztpraxis Neukölln

Jihan Saeed

Hermannstraße 52

12049 Berlin

Study site initiated 24.02.2025

Praxis Weichselstraße

Dr. med. Aliona Cuadrado

Weichselstr. 59

12045 Berlin

Study site initiated 18.02.2025

Eligibility criteria

Following the concept of pragmatic trials, we will keep the inclusion and exclusion criteria to a minimum to improve generalizability and enable the implementation of the intervention into routine care. Eligibility criteria for the GP practices were chosen to allow generalizability to the German primary care system.

Who will take informed consent?

Screening of potential study participants will be carried out in the study centers (GP practices) by the general practitioners based on the inclusion and exclusion criteria. Written informed consent will be obtained at the study centers by the GPs.

Additional consent provisions for collection and use of participant data and biological specimens

The patients can consent to being contacted by the study team for participation in semi-structured interviews as part of the qualitative process evaluation. Participating GPs, practice staff, link workers, study team and representatives of local community services will also be asked to participate in qualitative interviews.

Ethics approval and consent to participate

Ethics approval has been granted by the Institutional Review Board at Charité – Universitätsmedizin Berlin, reference number: EA1/104/24 (July 11^th 2024) and the ethics commission of the state medical association Brandenburg, reference number: 2024–94-BO (August 6^th 2024). The study will be carried out in accordance with the Helsinki Declaration and German Law. Written, informed consent to participate will be obtained from all participants.

Explanation for the choice of comparators

To be as pragmatic as possible we chose treatment-as-usual as comparator. However, to motivate persons in the control group to adhere to study procedures, we added a physical brochure to be sent out to the participants in the control group. These brochures contain information on local support to the TAU+ participants. In some of the communities, such brochures already exist. In communities without such an offer, we compiled a brochure together with local stakeholders.

Intervention description

Through Social Prescribing a GP can refer patients with non-medical health-related social needs to a so called “link worker”. A specifically trained professional with a background in a health or social profession. In the first step, the link worker assesses the needs of the patients and agrees with the patient on a goal. The link worker develops an action plan together with the patient. This action plans includes referrals to existing non-clinical support and services in the community. The link worker supports the patient to access the service agreed on. At the end of the intervention, the link worker provides written feedback to the prescribing GP [22]. The contact between link worker and patient usually involves several consultations over the course of several weeks (Table 1). The conceptual model for the intervention was adapted from Muhl et al. [14].

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Table 1. Description of the intervention using the TIDieR framework [23].

https://doi.org/10.1371/journal.pone.0322372.t001

Link workers will be trained before the intervention starts according to the SP link worker workforce development framework [24]. Link workers will have time to get to know the communities and present themselves not only to the GP practices, but also to the institutions providing local services. Link workers will build up an electronic database with local services and organizations where patients can potentially be referred to. Additionally, link workers will receive a communication training by an experienced staff member of the Institute of General Practice and Family Medicine and will have the opportunity of continuous supervision. There will also be case reviews each week.

Each study center will receive a training workshop to prepare for inclusion of participants and study procedures. Study nurses will receive training regarding baseline and follow-up data assessment to ensure a standardized assessment.

Criteria for discontinuing or modifying allocated interventions

Participants may withdraw from the programme at any time if they wish (even without giving reasons). GPs can withdraw patients at any time if they suspect that harm is inflicted though the intervention. Based on the monitoring reports made available to the Data Safety Monitoring Board (DSMB), it may recommend early termination of recruitment for the overall study or selected intervention groups.

Strategies to improve adherence to interventions

The alignment of the intervention delivery with the study protocol is verified in weekly case reviews with the link workers.

Relevant concomitant care permitted or prohibited during the trial

In both arms of the trial, medical care as usual by the GP and other providers will occur without any restrictions. At follow-up, we will ascertain health and social care provision to determine an influence of the intervention on care as usual in the control group and evaluate if individual randomization is feasible for a confirmatory trial.

Provisions for post-trial care

To our best knowledge, there are no reports of damages resulting from SP interventions. Therefore, we did not anticipate provisions for post-trial care.

Outcomes

The primary outcome is the feasibility of the trial measured by

1. (1). The proportion of participants who have at least one appointment with the link worker (intervention arm only) and
2. (2). The proportion of participants that drop out of the trial before the 6-month follow-up (attrition rate, both arms).

Secondary feasibility outcomes measured through questionnaires at 6-month follow-up and semi-structured interviews, as well as the trial documentation:

Acceptability:

• Satisfaction of GPs (questionnaire after last patient out) and of patients (6-month follow-up, intervention arm only) with the intervention;
• Acceptance of the intervention by patients (intervention arm only), GPs, link workers and local service providers as stated in qualitative interviews (subgroup).

Practicality:

• Proportion of eligible patients of all patients seen in the practice;
• Proportion of eligible patients excluded because of a language barrier;
• Proportion of eligible patients consenting to the randomized controlled trial;
• Proportion of consenting patients randomized and starting the intervention;
• Proportion of patients adhering to the appointments with link worker of these (intervention-arm only);
• Estimated time spent by GPs;

Demand/Utilization:

• Non-medical health related social problems assessed by GP:
• Non-medical health related social problems assessed by link worker;
• Frequency of link worker consultations per patient;
• Length of link worker visits per patient;
• Delivery mode of the link worker interaction (in person (home visit, in GP practice), phone);

Services recommended by the link worker

• Utilization of recommended non-clinical support and services by the patient.

Secondary clinical outcome measures (patient reported outcomes, PROMs) are assessed by computer assisted telephone interview at 3-months follow-up and 6-months follow-up.

Following the definition of SP by Muhl et al. [15], clinical endpoints are health (measured by WHODAS 2.0), well-being (measured by WHO-5, ICECAP-A and L-1) and community connection (assessed qualitatively). Patient questionnaires are kept to a minimum to avoid attrition. They consist of the following outcome measures (further information on content, validity, and reliability can be found in chapter Plans for assessment and collection of outcomes):

• Health status (WHODAS 2.0) [25,26];
• Subjective health status [27];
• Mental wellbeing (WHO-5) [28,29];
• Capability Wellbeing (ICECAP-A) [30];
• Health-related quality of life (EQ-5D-5L) [31];
• General life satisfaction (Short scale L-1 for recording general life satisfaction) [32,33];
• Loneliness (De Jong Gierveld Loneliness Short Scale) [34];
• Goal based outcome (GBO) [35–37];
• Resource use (relevant parts of PECUNIA RUM and EHIS-GeDA, decision on items was made referring to current systematic reviews [38–41]);
• Safety (Mortality, emergency department visits, unplanned hospital admissions, suicidality, suicide attempts, other adverse events).

Topics of the qualitative interviews are: Acceptance, practicability, need/use, implementation of the study, potentials and hurdles. For the patients, the integration into the neighbourhood will also be discussed.

Participant timeline

Patients will be recruited to the study during a GP consultation (t-1, cf. Fig 1, Fig 2). After baseline assessment and study arm allocation (t0), patients in the intervention arm will receive sessions with a link worker (s1-sn). 3 and 6 months after baseline we will conduct follow-up data assessments (t1, t2).

Sample size

Because this is an exploratory feasibility study without confirmatory hypothesis testing, we performed no formal sample size calculation. From prior experience, we assume that analyzing 215 participants in total (2:1 ratio: 143 in the SP arm and 72 in the TAU + arm) is sufficient to descriptively determine the feasibility and acceptance aspects of the trial and to obtain further information for the planning of the subsequent confirmatory trial.

Feasibility outcomes will be assessed depending on the type of outcome (e.g., n = 215 for attrition rates). In this patient group, a drop out of about 30% is expected, so that follow-up data for secondary clinical endpoints of 150 (n = 100 in the SP and n = 50 in the TAU + arm) patients can be assessed at 6-months follow-up (Fig 3).

For the qualitative study part, a total of n = 30–40 qualitative, semi-structured episodic interviews will be conducted with patients from the intervention and control groups (n = 15–20), as well as participating GPs, practice staff, link workers, study staff and representatives of local services (n = 15–20).

Recruitment

Based on the commitments of the participating GP practices, we expect it to be feasible to recruit more than 570 patients during a 6-month recruitment period. Thus, even considering lower recruitment due to external factors such as influenza epidemics, it is very well possible to recruit the 300 estimated patients in this feasibility trial.

Participating GP practices receive a compensation of 50 € per recruited patient.

Sequence generation

All patients who give consent for participation and who fulfil the inclusion criteria will be randomized.

The randomization code will be generated by an independent person (not otherwise involved in the study) as a block randomization (with variable block length) stratified by center (GP practice) with 2:1 allocation ratio. Thus, allocation will be conducted without any influence of the principal investigators, doctors, or link workers to obtain comparable treatment groups.

Concealment mechanism

Randomization codes will be obtained from the RedCap (Research Electronic Data Capture, version 14.0 or higher) database after entry of participant data, with the allocation being concealed.

Implementation

Participants will be enrolled by the GPs in the participating practices and will be allocated to the study groups by the study nurses.

Who will be blinded

This is an open study. Due to the nature of the study intervention, blinding is not possible for treating physicians, link workers, or patients. Due to the 2:1 allocation blinding of the biometrician is also not feasible.

Procedure for unblinding if needed

There is no blinding.

Plans for assessment and collection of outcomes

Data assessment is performed by study nurses independent from the intervention delivery and not located at the practices to minimize measurement bias. Computer-assisted telephone interviews by trained study nurses allow for decentralized data collection that caters to the needs of the vulnerable patient group which might not be capable to fill out questionnaires by themselves.

Feasibility outcomes will be collected through process parameters in the eCRF and trial documentation as well as qualitative interviews. Satisfaction is assessed through two questions for each group (General satisfaction with the service, recommendation of the service to friends and family).

The PROMS consist of the following questionnaires

• Health status (WHODAS 2.0)

The WHO Disability Assessment Schedule 2.0 is a generic patient reported outcome measure for health status. The domains of WHODAS 2.0 are based on the conceptual framework of the WHO’s International Classification of Functioning, Disability and Health (ICF), which has been the international standard for describing and measuring health and disability since 2001. All six ICF domains (Cognition, Mobility, Self-care, Social interaction, Life activities and Social participation) are covered by the WHODAS 2.0 tool. It shows high internal consistency, a high test-retest reliability as well as high validity in comparison with other instruments [25,26]. A computer adaptive form with 12 item version is available in German.

• Mental wellbeing (WHO-5)

The World Health Organization-Five Well-Being Index (WHO-5) is a short self-reported measure of current mental wellbeing. The scale has an adequate validity as an outcome measure in clinical trials [28] and normative data is available for a German version [29].

• General life satisfaction (Short scale L-1 for recording general life satisfaction):

The short scale L-1 for recording general life satisfaction consists of the item formulation established in SOEP [32,33]. The scale contains only one item with the following wording: “How satisfied are you at present, all in all, with your life”. The tool has been validated with a good reliability in German and normative data is available [33].

• Loneliness (De Jong Gierveld Loneliness Short Scale):

The short version of the De Jong Gierveld Loneliness Scale comprises 6 items and includes two subscales on emotional and social loneliness [34]. The questionnaire is valid and reliable. A validated German translation is available.

• Capability Wellbeing (ICECAP-A):

The ICEpop CAPability measure for Adults is a measure of well-being for the general adult population (aged 18 and over) for use in health economic evaluation. A validated German translation exists [30].

• Health-related quality of life (EQ-5D-5L):

The European Quality of Life 5 Dimensions 5 Level Version is a general instrument that can be used to assess the quality of life of patients regardless of their illness. It has been extensively validated, including in the German healthcare context [31].

• Subjective health status

Based on the European Health Interview and Examination Survey (EHIS) [27], the state of health is asked as follows: How is your health in general?

• Goal based outcome (GBO):

Link worker and participant agree on a main goal to be achieved through SP. The progress towards achieving this goal is measured using GBOs (“On a scale of zero to ten, please tell me the number that best describes how close you are to your goal today. Remember: zero means that you are as far away from your goal as you have ever been, and ten means that you have reached your goal completely.”) GBOs are proposed by two articles that assess appropriate outcomes for SP [42,43]. It is comparable to the Measure Yourself Concerns and Wellbeing (MYCaW®) outcome measure, which was validated in cancer care [35]. This outcome is highly relevant to patients because it is chosen by themselves and thus reflects the patient’s individual goals and values [36]. GBOs, such as MYCaW®, were assessed in several project reports identified in the systematic review by Napierala et al. [17], but no project provided enough data for further analysis. We found only one GBO in a feasibility study for children with autism spectrum disorder where it showed high levels of completion [37]. GBO will be measured in the intervention arm only.

• Resource use (relevant parts of PECUNIA RUM and EHIS-GeDA):

The PECUNIA Resource Use Measurement instrument (PECUNIA RUM) is a globally standardized, harmonized, and validated self-report tool for measuring resource use across various sectors, designed to facilitate costing from a societal viewpoint in the adult population [44]. This tool covers several relevant areas, including health and social care, education, justice, productivity losses, and informal care. In this study, we specifically employ selected items from this instrument that are pertinent to our examination of health and social care and productivity losses [38–41]. Where possible, the culturally adapted version from EHIS-GeDA is used for Germany.

The interviews of the qualitative study part will take place outside of everyday care at a later date on the basis of a separate invitation and consent. The interviews are conducted by trained members of the study team.

Plans to promote participant retention and complete follow-up

We expect to screen about 600 adult patients with at least one psychosocial need. Of these, about 300 patients (50%) will fulfil the eligibility criteria and consent to the trial. We assume that about 215 (around 70%) of these patients will be randomized (SP: 143 and TAU + : 72), as some participants cannot be reached, or withdraw their consent.

The population in question is a highly vulnerable group and the literature shows high rates of attrition [18]. Thus, the assumed rate of loss to follow-up is about 30% between baseline and 6-month follow-up (primary feasibility outcome), with around 2/3 of the loss-to-follow up attributed to the 3-month follow-up (Fig 3). For this study, loss to follow-up (and reasons for loss to follow up) are an essential part to assess the feasibility and will be assessed in detail if possible.

Data management

We will comply with relevant data protection laws (GDPR, local data protection laws). Data management is carried out in accordance with the specifications of the local quality management manual. The data is only stored and processed for the respective purpose.

In the informed consent form to participate in the study, the study participant authorizes the recording, processing and storage of his/her personal and medical data.

The collected data will be recorded and stored in the REDCap online database (REDCap = Research Electronic Data Capture, version 14.0 or higher) on a server of the Charité – Universitätsmedizin Berlin IT infrastructure in Germany.

The databases are only accessible to data management and authorised study personnel with individualised login. Personal identifying data of participants will be accessible only via 2-factor authentication.

The study data and study documents are archived for 10 years after the end of the study and all personally identifiable documents and data are then deleted. All research data will be anonymised 10 years after the end of the study.

Qualitative interviews are digitally recorded and transcribed using external transcription service providers. Tape recordings, transcribed protocols, questionnaires and data entry forms are stored on a protected area of the Charité server. Only authorized members of the study team have access.

Confidentiality

Personal identifying data (PiD) is entered into REDCap by the practice staff. The research data (RD) is collected and stored separately from the PiD in another independent REDCap project; no PiD is transmitted to the survey project.

The data is recorded in REDCap using pseudonyms, which consist of consecutive numbers without initials or dates of birth of the participants. The PiD database is the re-identification list for the pseudonymised FD entered into REDCap by the study personnel.

Pseudonymized health data will be entered online by the study staff into a REDCap database via an individualized link and a secure HTTPS Internet connection using encrypted transmission (SSL encryption). The data will be transmitted to the servers in encrypted form (via an HTTPS connection) immediately after completing the questionnaire and will not be stored on the computer or tablet.

Prior to enrolment in the study, study participants must sign a written informed consent for to the data collection, the transfer and the inspection by domestic supervisory authorities and authorized representatives who are bound to confidentiality (including study monitors and auditors).

Audio files and transcripts of the qualitative interviews are stored pseudonymously in a database on the protected server area of Charité - Universitätsmedizin Berlin, which is password-protected and only accessible to persons authorized by the principal investigator. Pseudonyms consist of consecutive numbers without initials or date of birth.

Plans for collection, laboratory evaluation and storage of biological specimens for genetic or molecular analysis in this trial/future use {33}

No biological specimens are collected as part of this study.

Statistical methods for primary and secondary outcomes

In this feasibility trial, all results will be interpreted exploratively. Details of the statistical analyses (including definition of analysis populations, subgroups, sensitivity analyses, etc.) will be pre-specified in a statistical analysis plan (SAP). Analyses will be performed using the Full Analysis Set (FAS), which is based on the intention-to-treat principle with all available data (i.e., missing data are not imputed).

The per-protocol population is defined as patients who adhere to the protocol (details are defined in the SAP). No interim analysis is planned

Interim analyses

No interim analysis is planned

Methods for additional analyses (e.g., subgroup analyses)

Sensitivity analyses include per-protocol-analysis based on patients complying with the protocol (as defined in the SAP) and subgroup analyses (i.e., gender; underlying psychosocial problem(s); age groups).

Methods in analysis to handle protocol non-adherence and any statistical methods to handle missing data

The analyses using the Full Analysis Set (FAS) are performed according to the intention-to-treat principle with all available data (missing data are not imputed).

The per-protocol population is defined as patients who adhere to the protocol (details are defined in the SAP).

Plans to give access to the full protocol, participant level-data and statistical code

An anonymized dataset will be made available in an open data repository (planned repository: Zenodo). The full study protocol can be found in the DRKS registry in German (DRKS00034654).

Composition of the coordinating centre and trial steering committee

Composition of the data monitoring committee, its role and reporting structure

The study will be monitored by two members of staff of the sponsor institution (Institute of General Practice and Family Medicine, Charité Universitätsmedizin Berlin): The continuous monitoring of the data received via REDCap will be performed by the study coordinator, the on-site monitoring visits will be performed by an additional member of staff, who is not directly involved in the study. The monitors will regularly send monitoring reports to the Data Safety Monitoring Board, in which they inform about the current recruitment status, deviations identified during the data and on-site monitoring, adverse events, and other issues in the conduct of the study. The first monitoring visit is supported by an independent co-monitor of the Clinical Trials Office of the Charité.

The data safety monitoring board (DSMB) consists of three experienced researchers, including a senior biometrician.

The aims of the DSMB are

1. -. to safeguard the interests of the study participants,
2. -. to assess the safety and efficacy of the intervention during the study and
3. -. monitoring the implementation of the study.

The DSMB receives and reviews information on the progress and data generated by the trial.

This includes:

1. assessing data quality, including completeness,
2. monitoring recruitment numbers and loss to follow up,
3. monitoring compliance with the protocol by participants and investigators,
4. the monitoring of adverse events,
5. monitoring compliance with previous DSMB recommendations,
6. considering the ethical implications of all DSMB recommendations.

The DSMB should decide whether to recommend continuing the recruitment of participants for the trial or to stop recruitment either for all or some treatment groups and/or for all treatment groups. participants should be stopped. The recommendations of the DSMB are advisory and not executive.

The composition of the DSMB, its working methods (including decision-making) and reporting are defined in a charter.

Adverse event reporting and harms

No adverse events associated with the intervention are described in the literature on social prescribing. However, a comprehensive monitoring procedure is established in accordance with ICH-GCP to demonstrate safety and safety, which consists of short-term notifications of individual case reports, periodic reports, safety monitoring by an independent data safety monitoring board (DSMB) and a comprehensive safety analysis of the study.

Frequency and plans for auditing trial conduct

The DFG (German Research Foundation) reserves the right to audit the study if necessary.

Plans for communicating important protocol amendments to relevant parties (e.g., trial participants, ethical committees)

Protocol amendments must be approved by the ethics committee of the Charité – Universitätsmedizin Berlin and the ethics commission of the state medical association Brandenburg. Changes are communicated to the funding body. The protocol will also be updated in the clinical trial registry (DRKS). Changes are communicated to all study personnel and study materials will be updated.

Dissemination plans

The results will be disseminated through international peer-reviewed articles in open access journals. The authorship guideline is available from the principal investigator upon reasonable request. The SPIRIT and CONSORT statements, with extensions for pragmatic trials, will be used for reporting of the protocol and trial, respectively. Further dissemination measures will include presentations at local and international conferences,

An anonymized dataset will be made available (Plans to give access to the full protocol, participant level-data and statistical code {31c}). The link worker training concept is available through Zenodo [48].

Trial status

Recruitment started on September 16^th, 2024. Recruitment is expected to close by May 31^st, 2025. Trial recruitment will continue until the sample size of 300 study participants will be recruited. Data collection is expected to be finished November 30^th 2025. Results are planned to be available May 31^st 2026.

This study protocol is version 1.2 from February 12^th, 2024.