Elsevier

Drug and Alcohol Dependence

Volume 154, 1 September 2015, Pages 125-131
Drug and Alcohol Dependence

Full length article
Evidence of continued injecting drug use after attaining sustained treatment-induced clearance of the hepatitis C virus: Implications for reinfection

https://doi.org/10.1016/j.drugalcdep.2015.06.032Get rights and content

Highlights

  • We followed-up a nationally representative cohort of 1170 people who inject drugs (PWID) who had attained sustained viral response (SVR).

  • Data linkage was used to examine injection-related morbidity/mortality events.

  • An increasing minority of our cohort had a post-SVR injection-related event.

  • Continued follow-up and promotion of harm reduction is warranted post-SVR in PWID.

  • The approach adopted here can be used to inform on trends in HCV reinfection risk.

Abstract

Background

People who inject drugs (PWID) are at the greatest risk of hepatitis C virus (HCV) infection, yet are often denied immediate treatment due to fears of on-going risk behaviour. Our principal objective was to examine evidence of continued injecting drug use among PWID following successful treatment for HCV and attainment of a sustained viral response (SVR).

Methods

PWID who attained SVR between 1992 and June 2012 were selected from the National Scottish Hepatitis C Clinical Database. Hospitalisation and mortality records were sourced for these patients using record linkage techniques. Our primary outcome variable was any hospitalisation or death, which was indicative of injecting drugs post-SVR.

Results

The cohort comprised 1170 PWID (mean age at SVR 39.6y; 76% male). The Kaplan Meier estimate of incurring the primary outcome after three years of SVR was 10.59% (95% CI, 8.75–12.79) After adjusting for confounding, the risk of an injection related hospital episode or death post-SVR was significantly increased with advancing year of SVR: AHR:1.07 per year (95% CI, 1.01–1.14), having a pre-SVR acute alcohol intoxication-related hospital episode: AHR:1.83 (95% CI, 1.29–2.60), and having a pre-SVR opiate or injection-related hospital episode: AHR:2.59 (95% CI, 1.84–3.64).

Conclusion

Despite attaining the optimal treatment outcome, these data indicate that an increasing significant minority of PWID continue to inject post-SVR at an intensity which leads to either hospitalisation or death and increased risk of reinfection.

Introduction

It is well established that people who inject drugs (PWID) are at the greatest risk of hepatitis C virus (HCV) infection. Globally, there are an estimated 16 million PWID who are currently injecting (Mathers et al., 2008) and of these, 10 million are estimated to have been infected with HCV (Nelson et al., 2011). Chronic HCV infection is a major cause of liver-related morbidity and mortality but can be cleared with antiviral treatment and establishment of sustained viral response (SVR). Currently, there is low initiation of HCV antiviral treatment among PWID, which likely relates to concerns of adherence to and reinfection post-treatment (Martin et al., 2013, Iversen and Maher, 2012). Regardless, recent studies have indicated treatment outcomes to be acceptable and risk of HCV reinfection to be relatively low among PWID, albeit based on only a few small-scale studies conducted among selected populations in clinical and harm reduction settings often with limited follow-up (Aspinall et al., 2013, Arain and Robaeys, 2014, Grady et al., 2013). Modelling work has further demonstrated that treating PWID is cost-effective and has the potential to reduce HCV transmission and prevalence in this population (Martin et al., 2011a, Martin et al., 2013). Therefore, recommendations state that treatment is not to be withheld from an individual based on injection status alone (EASL, 2015).

After being deemed one of the greatest public health challenges of our time, HCV was made a priority by the Scottish Government and a comprehensive Action Plan was formulated to curb the predominately injecting-related epidemic (Chisholm, 2004, Scottish Government Health Department, 2008). As a result, the overall number of people initiated on antiviral therapy in Scotland more than doubled between 2007 and 2010 with ∼1000 now treated per year and the vast majority (>80%) of these report having ever injected drugs (Health Protection Agency (HPA), 2013).

Given this recent and anticipated future upscale in treatment provision among PWID a better understanding is needed of the injecting risk behaviours and potential for reinfection post-SVR. Our principal objective, therefore, was to establish evidence and predictors of continued engagement in injection drug use post-SVR using a record-linkage approach involving both HCV treatment and injecting-related hospitalisation data for a large nationally representative cohort of over 1000 PWID.

Section snippets

Study population, data sources, and linkage procedure

This paper utilised a retrospective cohort of Scottish PWID derived from the HCV Clinical Database using data linked from four additional national databases. Health Protection Scotland (HPS) holds and maintains individual patient data for all HCV diagnosed persons who attended a specialist centre for HCV treatment and management across Scotland, referred to as the HCV Clinical Database. This database includes information on patient demographics, virology, treatment episodes, epidemiological

Sample characteristics (Table 1)

Table 1 displays the demographic and behavioural characteristics of the cohort with regard to our primary outcome (i.e., an injection-related hospital episode or death post-SVR). The average age at SVR was 39.6 years (standard deviation ± 8.2 years; range 19.0–67.7 years), and the majority were male (76%). The majority of the cohort (76%) attained SVR between 2006 and June 2012. A history of an IRH pre-SVR was found for 427 (37%) of the cohort, of which 222 had an IRH within three years prior to

Discussion

With highly effective but costly HCV treatments on the horizon and potential demand for treatment to increase particularly among the population who injects drugs, it is essential that the behaviours which pose a risk of reinfection post-SVR are well understood. There have been few small-scale studies examining engagement in injection drug use post-HCV antiviral treatment induced SVR. These studies rely on participation, accurate self-report by PWID, and have varied in respect of recruitment

Role of funding source

This project was supported by funding from the Scottish Government.

Contributors

HV performed the data analysis and interpretation under the supervision of JL, and drafted the paper under the supervision of SH and DG. SH and DG conceived, proposed, and oversaw the scope of the project. AW deterministically linked hospitalisation and mortality data with HCV Clinical and Diagnosis databases. All other authors provided clinical data, manuscript revisions, and approved final submission.

Conflict of interest statement

None declared.

Acknowledgements

Clinical Database Monitoring Committee, Clinical Database Managers, Data Entry Clerks, and HCV Clinical Leads who routinely monitor data which are entered onto the database. Health Protection Scotland, Information Services Division, Scotland, who hold all Scottish morbidity (hospitalisation) and mortality data, and who performed the initial linkage between the databases.

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