| Beliefs about capabilities | Acceptance of the truth, reality, or validity about an ability, talent, or facility that a person can put to constructive use | Patients’ perceived ability (or lack of) to find a healthcare provider | ✓ | ✓ |
| Patients’ perceived ability (or lack of) to integrate with the norms and rules within mainstream services | ✓ | ✓ |
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| Beliefs about consequences | Acceptance of the truth, reality, or validity about outcomes of a behaviour in a given situation | Patients’ beliefs about the consequences of not receiving health care | ✓ | ✓ |
| Consequences of continuity of care (or lack of) | ✓ | ✓ |
| Consequences of being discharged onto the streets with no primary care providers | | ✓ |
| Consequences of fragmented services on health | | ✓ |
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| Emotions | A complex reaction pattern, involving experiential, behavioural, and physiological elements by which the individual attempts to deal with a personally significant matter or event | Feelings of embarrassment when seeking health care | | ✓ |
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| Environmental context and resources | Any circumstance of a person’s situation or environment that discourages or encourages the development of skills and abilities, independence, social competence, and adaptive behaviour | Lack of patient ‘fixed abode’ and photographic ID | | ✓ |
| Signposting (or lack of) to appropriate services | ✓ | ✓ |
| Patients’ lack of resources to pay for public transport or make calls for appointments | | ✓ |
| Patients’ lack of resources to search services in their local areas | | ✓ |
| Availability (or lack of) facilities to promote medication adherence | ✓ | ✓ |
| Discharged from hospitals onto the streets | | ✓ |
| Unfavourable eligibility criteria for access to substance misuse and mental health services | ✓ | |
| Facilitated registration for primary care services through temporary shelters | ✓ | |
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| Goals and intentions | Mental representations of outcomes or end states that an individual wants to achieve | Patients’ intentions to seek health care | ✓ | ✓ |
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| Knowledge | An awareness of the existence of something | Patients’ knowledge/lack of knowledge of mainstream services available in their area | ✓ | ✓ |
| Patients’ knowledge/lack of knowledge of SPHCPH for people who are homeless available in their areas | ✓ | ✓ |
| Patients’ lack of knowledge of the rules and policies of mainstream practices | ✓ | ✓ |
| Lack of knowledge among mainstream frontline staff about eligibility for registration of patients who are homeless | | ✓ |
| GPs’ knowledge/lack of knowledge of the complexity of patients’ health conditions | ✓ | ✓ |
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| Memory, attention, and decision processes | The ability to retain information, focus selectively on aspects of the environment, and choose between ≥2 alternatives | Committing crime to go to prison to access health care | | ✓ |
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| Reinforcement | Increasing the probability of a response by arranging a dependent relationship, or contingency, between the response and a given stimulus | Proactive follow-up of patients at the SPHCHP | ✓ | |
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| Skills | An ability or proficiency acquired through practice | Patients’ lack of skills in completing paperwork and navigating through the system | | ✓ |
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| Social influences | Those interpersonal processes that can cause individuals to change their thoughts, feelings, or behaviours | Support from friends and families in registration process | ✓ | |
| Social network to facilitate appointments and engagement | ✓ | |
| Perceived stigma and discrimination from other patients | | ✓ |
| Perceived stigma and discrimination from healthcare staff | | ✓ |
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| Social/professional role and identity | A coherent set of behaviours and displayed personal qualities of an individual in a social or work setting | Trust (or lack of) between healthcare staff and patients | ✓ | ✓ |
| Self-identity as a person who is homeless | | ✓ |
| Poor handover of patient information across healthcare professionals and settings | | ✓ |