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Comment
. 2015 May 15;29(8):965-73.
doi: 10.1097/QAD.0000000000000642.

The causal effect of opioid substitution treatment on HAART medication refill adherence

Bohdan Nosyk  1 , Jeong E Min, Guillaume Colley, Viviane D Lima, Benita Yip, M-J S Milloy, Evan Wood, Julio S G Montaner
Affiliations
Comment

The causal effect of opioid substitution treatment on HAART medication refill adherence

Bohdan Nosyk et al. AIDS. .

Abstract

Background: People who inject drugs (PWID) account for roughly 13% of the prevalent HIV/AIDS population outside of sub-Saharan Africa, and access to opioid substitution treatment (OST) is limited in many settings globally. OST likely facilitates access to HAART, yet sparse evidence is available to support this hypothesis. Our objective was to determine the causal impact of OST exposure on HAART adherence among HIV-positive PWID in a Canadian setting.

Methods: We executed a retrospective cohort study using linked population-level data for British Columbia, Canada (January 1996-March 2010). We considered HIV-positive PWID after meeting HAART initiation criteria. A marginal structural model was estimated on a monthly timescale using inverse probability of treatment weights. The primary outcome was 95% HAART adherence, according to pharmacy refill compliance. Exposure to OST was defined as 95% of OST receipt, and we controlled for a range of fixed and time-varying covariates.

Results: Our study included 1852 (63.3%) HIV-positive PWID with a median follow-up of 5.5 years; 34% were female and 39% had previously accessed OST. The baseline covariate-adjusted odds of HAART adherence following OST exposure was 1.96 (95% confidence interval: 1.72-2.24), although the adjusted odds estimated within the marginal structural model was 1.68 (1.48-1.92). Findings were robust to sensitivity analyses on model specification.

Conclusion: In a setting characterized by universal healthcare and widespread access to both office-based OST and HAART, OST substantially increased the odds of HAART adherence. This underlines the need to address barriers to OST globally to reduce the disease burden of both opioid dependence and HIV/AIDS.

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Conflict of interest statement

Conflicts of interest

There are no conflicts of interest.

Figures

Fig. 1
Fig. 1. Directed acyclic graph illustrating the hypothesized causal relationship between time-varying opioid substitution treatment and HAART exposure
C, confounding factors, including time-invariant and time-varying covariates; E, exposure to OST; O, outcome, HAART adherence.
Fig. 2
Fig. 2. Study sample selection
OST, opioid substitution treatment; PWID, people who inject drugs.
See this image and copyright information in PMC

Comment on

References

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