Table 1 Domains and corresponding items measured in baseline and follow-up surveys given to study participants

Primary Exposures

OPC use

In the past 30 days: used an OPC, name of OPCs used, frequency of use, proportion of drug use consumed at OPC

Primary Outcomes

Overdose

Lifetime and past 30-day nonfatal overdose

Hepatitis C

Lifetime and past 6-month hepatitis C test result, past 6-month positive hepatitis C diagnosis, receipt of treatment

HIV

Lifetime and past 6-month HIV test result, past 6-month positive HIV diagnosis, receipt of ARV and PrEP

Other infections

Past 6-month skin and soft tissue infections, mode of treatment for infection, past 6-month diagnosis of endocarditis

Healthcare use

Past 6-month: number of times used the emergency room to access health care; number of nights spent in the hospital

Harm reduction service use

Year and month of first use; type of services used and frequency of use in the past 3 months

Substance use disorder treatment

Past 6-month: referral to treatment; source of referral; enrollment in treatment; current status of enrollment

Confounders

Drug use

Lifetime, past 30 day, and past 7 day self-reported by type of drug and mode of use

Injection practices

Past 30 days and past 7-day injection practices

Reasons for using OPC

No safe place to use, prior overdose, change in drug dealer, concern about safety of the supply

Syringe disposal

In the past 30 days, number of days: disposed of syringes in a public place; in a hazardous waste container

Demographics

Age, sex, gender identity, race and ethnicity, education

Socioeconomic status

Housing status, zip code, employment, income, money in exchange for sexual activities

Criminal legal system

Past 30 days: number of times stopped by police, arrested, held overnight in jail or prison

Health-related quality of life

Physical function, ability to participate in social roles and activities, depression, anxiety, fatigue, sleep disturbance, pain