Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico.
Patterns of polydrug use among people who inject drugs (PWID) may be differentially associated with overdose and unique human immunodeficiency virus (HIV) risk factors. Subgroups of PWID in Tijuana, Mexico, were identified based on substances used, route of administration, frequency of use and co-injection indicators.



Participants were PWID residing in Tijuana age ≥18 years sampled from 2011 to 2012 who reported injecting an illicit substance in the past month (n = 735). Latent class analysis identified discrete classes of polydrug use characterised by 11 indicators of past 6 months substance use. Multinomial logistic regression examined class membership association with HIV risk behaviours, overdose and other covariates using an automated three-step procedure in mplus to account for classification error.



Participants were classified into five subgroups. Two polydrug and polyroute classes were defined by use of multiple substances through several routes of administration and were primarily distinguished from each other by cocaine use (class 1: 5%) or no cocaine use (class 2: 29%). The other classes consisted primarily of injectors: cocaine, methamphetamine and heroin injection (class 3: 4%); methamphetamine and heroin injection (class 4: 10%); and heroin injection (class 5: 52%). Compared with the heroin-only injection class, memberships in the two polydrug and polyroute use classes were independently associated with both HIV injection and sexual risk behaviours.



Substance use patterns among PWID in Tijuana are highly heterogeneous, and polydrug and polyroute users are a high-risk subgroup who may require more tailored prevention and treatment interventions. [Meacham MC, Roesch SC, Strathdee SA, Lindsay S, Gonzalez-Zuniga P, Gaines TL. Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico. Drug Alcohol Rev 2018;37:128-136].
Department of Psychiatry, University of California San Francisco, San Francisco, USA.|Division of Global Public Health, University of California San Diego, San Diego, USA.|Graduate School of Public Health, San Diego State University, San Diego, USA.
Meredith C
MC
Meacham
Department of Psychology, San Diego State University, San Diego, USA.
Scott C
SC
Roesch
Division of Global Public Health, University of California San Diego, San Diego, USA.
Steffanie A
SA
Strathdee
Graduate School of Public Health, San Diego State University, San Diego, USA.
Suzanne
S
Lindsay
Division of Global Public Health, University of California San Diego, San Diego, USA.
Patricia
P
Gonzalez-Zuniga
Division of Global Public Health, University of California San Diego, San Diego, USA.
Tommi L
TL
Gaines
D000328:Adult; D062787:Drug Overdose; D055030:Drug Users; D005260:Female; D015658:HIV Infections / Q000209:etiology*; D006801:Humans; D008297:Male; D008800:Mexico; D008875:Middle Aged; D016485:Needle Sharing / Q000009:adverse effects*; D012307:Risk Factors; D012309:Risk-Taking; D015819:Substance Abuse, Intravenous / Q000150:complications*
HIV risk behaviour; PWID; latent class analysis; polydrug; polyroute