Table 1 Candidate predictor variables

Age

Continuous

Sex

Binary:

1: Male

2: Female

Injecting status

Categorical:

1: Currently injecting

2. Previously injected (but not currently)

3: Never injected

HIV positivity

Binary:

1: Yes

2: No

Hepatitis C RNA positivity

Binary:

1: Positive

2: Negative (never infected or cleared by treatment)

Polysubstance use:

Current number of substances used problematically

Count

Problematic alcohol use

Binary:

1: Any current problematic use of alcohol

2: No current problematic use of alcohol

Problematic

benzodiazepine use

Binary:

1. Any current problematic use of any benzodiazepine

2. No current problematic use of any benzodiazepine

Housing status

Categorical:

1: No fixed abode—urgent housing problem, i.e

-—Lives on streets/rough sleeper

-—Uses night shelter (night-by-night basis) /emergency hostels

-—Sofa surfing/sleeps on different friend’s floor each night

2: Housing problem, i.e

- Staying with friends/family as a short-term guest

- Night winter shelter

- Direct access short stay hostel

- Short-term B & B or other hotel

- Placed in temporary accommodation by the Local Authority

- Squatting

3: No housing problem

- Owner-occupier

- Tenant—private landlord/ housing association/ Local

- Authority/registered landlord/arm’s length management organisation

- Approved premises

- Supported housing/hostel

- Traveller

- Own property

- Settled mainstream housing with friends/family

- Shared ownership scheme

Recent acute inpatient hospital admission

Binary:

1. Inpatient acute hospital admission within the last 6 months

2. No acute inpatient hospital admissions within the last 6 months

Recent mental health inpatient hospital admission

Binary:

1. Inpatient mental health hospital admission within the last 6 months

2. No inpatient mental health hospital admissions within the last 6 months

Recent history of incarceration

Binary:

1. Referred to the drug service from prison

2. Referred to the drug service by any other source