Prevalence of opioid dependence in New South Wales, Australia, 2014-16: Indirect estimation from multiple data sources using a Bayesian approach

AIMS

To estimate the prevalence of, and number of unobserved people with opioid dependence by sex and age group in New South Wales (NSW), Australia.

DESIGN

We applied a Bayesian statistical modelling approach to opioid agonist treatment records linked to adverse event rate data. We estimated prevalence from three types of adverse event separately: opioid mortality, opioid-poisoning hospitalizations and opioid-related charges. We extended the model and produced prevalence estimates from a 'multi-source' model based on all three types of adverse event data.

SETTING, PARTICIPANTS AND MEASUREMENTS

This study was conducted in NSW, Australia, 2014-16 using data from the Opioid Agonist Treatment and Safety (OATS) study, which included all people who had received treatment for opioid dependence in NSW. Aggregate data were obtained on numbers of adverse events in NSW. Rates of each adverse event type within the OATS cohort were modelled. Population data were provided by State and Commonwealth agencies.

FINDINGS

Prevalence of opioid dependence among those aged 15-64 years in 2016 was estimated to be 0.96% (95% credible interval [CrI] = 0.82%, 1.12%) from the mortality model, 0.75% (95% CrI = 0.70%, 0.83%) from hospitalizations, 0.95% (95% CrI = 0.90%, 0.99%) from charges and 0.92% (95% CrI = 0.88%, 0.96%) from the multi-source model. Of the estimated 46 460 (95% CrI = 44 680, 48 410) people with opioid dependence in 2016 from the multi-source model, approximately one-third (16 750, 95% CrI = 14 960, 18 690) had no record of opioid agonist treatment within the last 4 years. From the multi-source model, prevalence in 2016 was estimated to be 1.24% (95% CrI = 1.18%, 1.31%) in men aged 15-44, 1.22% (95% CrI = 1.14%, 1.31%) in men 45-64, 0.63% (95% CrI = 0.59%, 0.68%) in women aged 15-44 and 0.56% (95% CrI = 0.50%, 0.63%) in women aged 45-64.

CONCLUSIONS

A Bayesian statistical approach to estimate prevalence from multiple adverse event types simultaneously calculates that the estimated prevalence of opioid dependence in NSW, Australia in 2016 was 0.92%, higher than previous estimates.

Counselling behavioural interventions for HIV, STI and viral hepatitis among key populations: a systematic review of effectiveness, values and preferences, and cost studies

INTRODUCTION

Key populations (sex workers, men who have sex with men, people who inject drugs, people in prisons and other closed settings, and trans and gender diverse individuals) are disproportionately affected by HIV, sexually transmitted infections (STIs) and viral hepatitis (VH). Counselling behavioural interventions are widely used, but their impact on HIV/STI/VH acquisition is unclear.

METHODS

To inform World Health Organization guidelines, we conducted a systematic review and meta-analysis of effectiveness, values and preferences, and cost studies about counselling behavioural interventions with key populations. We searched CINAHL, PsycINFO, PubMed and EMBASE for studies published between January 2010 and December 2022; screened abstracts; and extracted data in duplicate. The effectiveness review included randomized controlled trials (RCTs) with HIV/STI/VH incidence outcomes; secondary review outcomes of unprotected sex, needle/syringe sharing and mortality were captured if studies also included primary review outcomes. We assessed the risk of bias using the Cochrane Collaboration tool, generated pooled risk ratios through random effects meta-analysis and summarized findings in GRADE evidence profiles. Values and preferences and cost data were summarized descriptively.

RESULTS

We identified nine effectiveness, two values and preferences, and two cost articles. Meta-analysis of six RCTs showed no statistically significant effect of counselling behavioural interventions on HIV incidence (1280 participants; combined risk ratio [RR]: 0.70, 95% confidence interval [CI]: 0.41-1.20) or STI incidence (3783 participants; RR: 0.99; 95% CI: 0.74-1.31). One RCT with 139 participants showed possible effects on hepatitis C virus incidence. There was no effect on secondary review outcomes of unprotected (condomless) sex (seven RCTs; 1811 participants; RR: 0.82, 95% CI: 0.66-1.02) and needle/syringe sharing (two RCTs; 564 participants; RR 0.72; 95% CI: 0.32-1.63). There was moderate certainty in the lack of effect across outcomes. Two values and preferences studies found that participants liked specific counselling behavioural interventions. Two cost studies found reasonable intervention costs.

DISCUSSION

Evidence was limited and mostly on HIV, but showed no effect of counselling behavioural interventions on HIV/VH/STI incidence among key populations.

CONCLUSIONS

While there may be other benefits, the choice to provide counselling behavioural interventions for key populations should be made with an understanding of the potential limitations on incidence outcomes.

Risk factors and genotype distribution of hepatitis C virus in Georgia: A nationwide population-based survey

In preparation for the National Hepatitis C Elimination Program in the country of Georgia, a nationwide household-based hepatitis C virus (HCV) seroprevalence survey was conducted in 2015. Data were used to estimate HCV genotype distribution and better understand potential sex-specific risk factors that contribute to HCV transmission. HCV genotype distribution by sex and reported risk factors were calculated. We used explanatory logistic regression models stratified by sex to identify behavioral and healthcare-related risk factors for HCV seropositivity, and predictive logistic regression models to identify additional variables that could help predict the presence of infection. Factors associated with HCV seropositivity in explanatory models included, among males, history of injection drug use (IDU) (aOR = 22.4, 95% CI = 12.7, 39.8) and receiving a blood transfusion (aOR = 3.6, 95% CI = 1.4, 8.8), and among females, history of receiving a blood transfusion (aOR = 4.0, 95% CI 2.1, 7.7), kidney dialysis (aOR = 7.3 95% CI 1.5, 35.3) and surgery (aOR = 1.9, 95% CI 1.1, 3.2). The male-specific predictive model additionally identified age, urban residence, and history of incarceration as factors predictive of seropositivity and were used to create a male-specific exposure index (Area under the curve [AUC] = 0.84). The female-specific predictive model had insufficient discriminatory performance to support creating an exposure index (AUC = 0.61). The most prevalent HCV genotype (GT) nationally was GT1b (40.5%), followed by GT3 (34.7%) and GT2 (23.6%). Risk factors for HCV seropositivity and distribution of HCV genotypes in Georgia vary substantially by sex. The HCV exposure index developed for males could be used to inform targeted testing programs.

Developing and Piloting a Standardized European Protocol for Hepatitis C Prevalence Surveys in the General Population (2016-2019)

Background: A robust estimate of the number of people with chronic hepatitis C virus (HCV) infection is essential for an appropriate public health response and for monitoring progress toward the WHO goal of eliminating viral hepatitis. Existing HCV prevalence studies in the European Union (EU)/European Economic Area (EEA) countries are heterogeneous and often of poor quality due to non-probability based sampling methods, small sample sizes and lack of standardization, leading to poor national representativeness. This project aimed to develop and pilot standardized protocols for undertaking nationally representative HCV prevalence surveys in the general adult population.

Methods: From 2016 to 2019 a team from the Robert Koch-Institute contracted by the European Centre for Disease Prevention and Control synthesized evidence on existing HCV prevalence surveys and survey methodology and drafted a protocol. The methodological elements of the protocol were piloted and evaluated in Bulgaria, Finland and Italy, and lessons learnt from the pilots were integrated in the final protocol. An international multidisciplinary expert group was consulted regularly.

Results: The protocol includes three alternative study approaches: a stand-alone survey; a “nested” survey within an existing health survey; and a retrospective testing survey approach. A decision algorithm advising which approach to use was developed. The protocol was piloted and finalized covering minimum and gold standards for all steps to be implemented from sampling, data protection and ethical issues, recruitment, specimen collection and laboratory testing options, staff training, data management and analysis and budget considerations. Through piloting, the survey approaches were effectively implemented to produce HCV prevalence estimates and the pilots highlighted the strengths and limitations of each approach and key lessons learnt were used to improve the protocol.

Conclusions: An evidence-based protocol for undertaking HCV prevalence serosurveys in the general population reflecting the different needs, resources and epidemiological situations has been developed, effectively implemented and refined through piloting. This technical guidance supports EU/EEA countries in their efforts to estimate their national hepatitis C burden as part of monitoring progress toward the elimination targets.

Allocating treatment resources for hepatitis C in the UK: a constrained optimization modelling approach

Background and objective: Although the treatment of chronic hepatitis C (CHC) has significantly evolved with the introduction of direct-acting antivirals, the treatment uptake rates have been low especially among marginalized groups in the UK, such as people who inject drug (PWID) and men who have sex with men (MSM). Cutting health inequality is a major focus of healthcare agencies. This study aims to identify the optimal allocation of treatment budget for chronic hepatitis CHC among populations and treatments in the UK so that liver-related mortality in patients with CHC is minimized, given the constraint of treatment budget and equity issue. Methods: A constrained optimization modelling of resource allocation for the treatment of CHC was developed in Excel from the perspective of the UK National Health System over a lifetime horizon. The model was designated with the objective function of minimizing liver-related deaths by varying the decision variables, representing the number of patients receiving each treatment (elbasvir-grazoprevir, ombitasvir-paritaprevir-ritonavir-dasabuvir, sofosbuvir-ledipasvir, and pegylated interferon-ribavirin) in each population (the general population, PWID, and MSM). Two main constraints were formulated including treatment budget and the issue of equity. The model was populated with UK local data applying linear programming and underwent internal and external validation. Scenario analyses were performed to assess the robustness of model results. Results: Within the constraints of no additional funding over original spending in status quo and the consideration of the issue of equity among populations, the optimal allocation from the constrained optimization modelling (treating 13,122 PWID, 160 MSM, and 904 general patients with ombitasvir-paritaprevir-ritonavir-dasabuvir) was found to treat 2,430 more patients (relative change: 20.7%) and avert 78 liver-related deaths (relative change: 0.3%) compared with the current allocation. The number of patients receiving treatment increased 4,928 (relative change: 60.1%) among PWID and 42 (relative change: 35.8%) among MSM. Conclusion: The current allocation of treatment budget for CHC is not optimal in the UK. More patients would be treated, and more liver-related deaths would be avoided using a new allocation from a constrained optimization modelling without incurring additional spending and considering the issue of equity.

Evaluating the power of the causal impact method in observational studies of HCV treatment as prevention

OBJECTIVES

The causal impact method (CIM) was recently introduced for evaluation of binary interventions using observational time-series data. The CIM is appealing for practical use as it can adjust for temporal trends and account for the potential of unobserved confounding. However, the method was initially developed for applications involving large datasets and hence its potential in small epidemiological studies is still unclear. Further, the effects that measurement error can have on the performance of the CIM have not been studied yet. The objective of this work is to investigate both of these open problems.

METHODS

Motivated by an existing dataset of HCV surveillance in the UK, we perform simulation experiments to investigate the effect of several characteristics of the data on the performance of the CIM. Further, we quantify the effects of measurement error on the performance of the CIM and extend the method to deal with this problem.

RESULTS

We identify multiple characteristics of the data that affect the ability of the CIM to detect an intervention effect including the length of time-series, the variability of the outcome and the degree of correlation between the outcome of the treated unit and the outcomes of controls. We show that measurement error can introduce biases in the estimated intervention effects and heavily reduce the power of the CIM. Using an extended CIM, some of these adverse effects can be mitigated.

CONCLUSIONS

The CIM can provide satisfactory power in public health interventions. The method may provide misleading results in the presence of measurement error.

Estimating the prevalence of problem drug use from drug-related mortality data

BACKGROUND AND AIMS

Indirect estimation methods are required for estimating the size of populations where only a proportion of individuals are observed directly, such as problem drug users (PDUs). Capture-recapture and multiplier methods are widely used, but have been criticized as subject to bias. We propose a new approach to estimating prevalence of PDU from numbers of fatal drug-related poisonings (fDRPs) using linked databases, addressing the key limitations of simplistic 'mortality multipliers'.

METHODS

Our approach requires linkage of data on a large cohort of known PDUs to mortality registers and summary information concerning additional fDRPs observed outside this cohort. We model fDRP rates among the cohort and assume that rates in unobserved PDUs are equal to rates in the cohort during periods out of treatment. Prevalence is estimated in a Bayesian statistical framework, in which we simultaneously fit regression models to fDRP rates and prevalence, allowing both to vary by demographic factors and the former also by treatment status.

RESULTS

We report a case study analysis, estimating the prevalence of opioid dependence in England in 2008/09, by gender, age group and geographical region. Overall prevalence was estimated as 0.82% (95% credible interval = 0.74-0.94%) of 15-64-year-olds, which is similar to a published estimate based on capture-recapture analysis.

CONCLUSIONS

Our modelling approach estimates prevalence from drug-related mortality data, while addressing the main limitations of simplistic multipliers. This offers an alternative approach for the common situation where available data sources do not meet the strong assumptions required for valid capture-recapture estimation. In a case study analysis, prevalence estimates based on our approach were surprisingly similar to existing capture-recapture estimates but, we argue, are based on a much more objective and justifiable modelling approach.

Detection, stratification and treatment of hepatitis C-positive prisoners in the United Kingdom prison estate: Development of a pathway of care to facilitate the elimination of hepatitis C in a London prison

The United Kingdom is committed to eliminating hepatitis C virus (HCV) infection by 2025. The prison estate provides an opportunity to identify and treat HCV-positive individuals in a high-prevalence environment. We designed and implemented a pathway of care within a London prison to diagnose, stratify and link HCV-positive prisoners into care. This study was a two-phase case study of a HCV care pathway. New arrivals to the prison were offered blood-borne virus screening with dried blood spot testing at their secondary health check. Those with active infection completed disease stratification tests and were reviewed at a weekly hospital-based multidisciplinary team meeting to determine management. In Phase-2, the pathway was redesigned to improve testing and the referral of HCV-positive prisoners into treatment. Over the 30-month evaluation period, 12,946 people were received in the prison. During Phase-1, 19.6% of new arrivals completed blood-borne virus testing, with 7.3% identified as HCV-positive. Just 8.3% of HCV-positive individuals were treated or referred for treatment in Phase-1. During Phase-2, 30% of new receptions completed BBV testing and 3.9% were identified as HCV-positive. Linkage into care was improved, with 38.9% treated or referred during the second phase. Poor access to testing and referral to treatment limit the effectiveness of care provision for prisoners with HCV. Elimination of HCV in prisons requires local service configuration to ensure high uptake of testing, with all HCV-positive cases then offered treatment during custody or referral on to treatment after release.

High prevalence of Hepatitis C Virus infection among people who use crack cocaine in an important international drug trafficking route in Central-West Region Brazil

In this study, the prevalence rate, associated risk factors and genetic diversity of hepatitis C virus (HCV) infection were determined among people who use crack from an international drug trafficking route in Central-West, Brazil. Blood samples were collected from 700 users of crack from Campo Grande and two border cities of Mato Grosso do Sul State and tested for HCV infection using serological and molecular testing methodologies. Anti-HCV was detected in 31/700 (4.5%, 95% CI: 2.9-6.0%) and HCV RNA in 26/31 (83.9%) of anti-HCV positive samples. Phylogenetic analysis of three HCV sub-genomic regions (5'UTR, NS5B and HVR-1) revealed the circulation of 1a (73.9%), 1b (8.7%) and 3a (17.4%) genotypes. Next-generation sequencing and phylogenetic analysis of intra-host viral populations of HCV HVR-1 showed a significant variation in intra-host genetic diversity among infected individuals, with 58.8% composed of more than one sub-population. Bayesian analysis estimated that the most recent common HCV ancestor for strains identified here was introduced to this region after 1975 following expansion of intravenous drug use in Brazil. Multivariate analyses showed that only 'ever having injected drugs' was independently associated with HCV infection. These results indicate an increasing spread of multiple HCV strains requiring public health intervention, such as harm reduction, testing services and treatment among crack users in this important border region of Central Brazil.

The Relationship Between Perception of HIV Susceptibility and Willingness to Discuss PrEP With a Health Care Provider: A Pilot Study

HIV continues to be a significant public health concern and despite recent reductions in new HIV diagnoses, certain demographics continue to be disproportionality affected. Men who have sex with other men (MSM) account for the largest percentage of new HIV diagnoses; however, 24% of new diagnoses can be attributed to male-to-female sex, highlighting the need to explore the HIV epidemic beyond the narrow scope of MSM. A multivariate linear regression model was used to explore the perception of HIV susceptibility and level of comfort discussing pre-exposure prophylaxis (PrEP) with a health care provider among a sample of men living in the United States (n = 377). Men who had an increased perception of HIV susceptibility were significantly more likely to feel comfortable discussing PrEP with a health care provider. Men who distinguish themselves to be at increased risk of acquiring HIV were significantly more likely to report having either insertive or receptive condomless anal intercourse within the previous 3 months, while men who reported condomless vaginal intercourse perceived low HIV susceptibility. Never being screened for HIV was significantly associated with a perception of low HIV susceptibility compared to those men who had been screened in the previous year. Understanding how men perceive HIV susceptibility and engage with HIV prevention may help to improve HIV prevention efforts such as PrEP.

Evaluating the population impact of hepatitis C direct acting antiviral treatment as prevention for people who inject drugs (EPIToPe) - a natural experiment (protocol)

INTRODUCTION

Hepatitis C virus (HCV) is the second largest contributor to liver disease in the UK, with injecting drug use as the main risk factor among the estimated 200 000 people currently infected. Despite effective prevention interventions, chronic HCV prevalence remains around 40% among people who inject drugs (PWID). New direct-acting antiviral (DAA) HCV therapies combine high cure rates (>90%) and short treatment duration (8 to 12 weeks). Theoretical mathematical modelling evidence suggests HCV treatment scale-up can prevent transmission and substantially reduce HCV prevalence/incidence among PWID. Our primary aim is to generate empirical evidence on the effectiveness of HCV 'Treatment as Prevention' (TasP) in PWID.

METHODS AND ANALYSIS

We plan to establish a natural experiment with Tayside, Scotland, as a single intervention site where HCV care pathways are being expanded (including specialist drug treatment clinics, needle and syringe programmes (NSPs), pharmacies and prison) and HCV treatment for PWID is being rapidly scaled-up. Other sites in Scotland and England will act as potential controls. Over 2 years from 2017/2018, at least 500 PWID will be treated in Tayside, which simulation studies project will reduce chronic HCV prevalence among PWID by 62% (from 26% to 10%) and HCV incidence will fall by approximately 2/3 (from 4.2 per 100 person-years (p100py) to 1.4 p100py). Treatment response and re-infection rates will be monitored. We will conduct focus groups and interviews with service providers and patients that accept and decline treatment to identify barriers and facilitators in implementing TasP. We will conduct longitudinal interviews with up to 40 PWID to assess whether successful HCV treatment alters their perspectives on and engagement with drug treatment and recovery. Trained peer researchers will be involved in data collection and dissemination. The primary outcome - chronic HCV prevalence in PWID - is measured using information from the Needle Exchange Surveillance Initiative survey in Scotland and the Unlinked Anonymous Monitoring Programme in England, conducted at least four times before and three times during and after the intervention. We will adapt Bayesian synthetic control methods (specifically the Causal Impact Method) to generate the cumulative impact of the intervention on chronic HCV prevalence and incidence. We will use a dynamic HCV transmission and economic model to evaluate the cost-effectiveness of the HCV TasP intervention, and to estimate the contribution of the scale-up in HCV treatment to observe changes in HCV prevalence. Through the qualitative data we will systematically explore key mechanisms of TasP real world implementation from provider and patient perspectives to develop a manual for scaling up HCV treatment in other settings. We will compare qualitative accounts of drug treatment and recovery with a 'virtual cohort' of PWID linking information on HCV treatment with Scottish Drug treatment databases to test whether DAA treatment improves drug treatment outcomes.

ETHICS AND DISSEMINATION

Extending HCV community care pathways is covered by ethics (ERADICATE C, ISRCTN27564683, Super DOT C Trial clinicaltrials.gov: NCT02706223). Ethical approval for extra data collection from patients including health utilities and qualitative interviews has been granted (REC ref: 18/ES/0128) and ISCRCTN registration has been completed (ISRCTN72038467). Our findings will have direct National Health Service and patient relevance; informing prioritisation given to early HCV treatment for PWID. We will present findings to practitioners and policymakers, and support design of an evaluation of HCV TasP in England.

The Hepatitis C Awareness Through to Treatment (HepCATT) study: improving the cascade of care for hepatitis C virus-infected people who inject drugs in England

BACKGROUND AND AIMS

Previous studies have shown low rates of diagnosis and treatment of hepatitis C virus (HCV) infection in people who inject drugs (PWID). Our aims were to test the effect of a complex intervention [Hepatitis C Awareness Through to Treatment (HepCATT)] in drug and alcohol clinics-primarily, on engagement of HCV-positive PWID with therapy and, secondarily, on testing for HCV, referral to hepatology services and start of HCV treatment.

DESIGN AND SETTING

A non-randomized pilot study in three specialist addiction clinics in England comparing an intervention year (starting between September 2015 and February 2016) with a baseline year (2014), together with three control clinics.

PARTICIPANTS

Analysis included all attendees at the intervention and control specialist addiction clinics identified as PWID.

INTERVENTION

The intervention comprised the placement of a half-time facilitator in each clinic for 12 months with the brief to increase diagnosis of HCV infection within clients at those services and the engagement of diagnosed individuals with an appropriate care pathway. The facilitator undertook various activities, which could include training of key workers, direct interaction with clients, streamlining and support for hepatology appointments and introduction of dried blood-spot testing.

MEASUREMENTS

For each clinic and period, we obtained the total number of clients and, as relevant, their status as PWID, tested for HCV, known HCV-positive, engaged with HCV therapy or treated.

FINDINGS

Compared with baseline, there was strong evidence that engagement with HCV therapy in the intervention year increased (P < 0.001) more in the HepCATT centres than controls, up ⁺ 31 percentage points [95% confidence interval (CI) = 19-43] versus -12 (CI = -31 to ⁺ 6) and odds ratio (OR) = 9.99 (CI = 4.42-22.6) versus 0.35 (CI = 0.08-1.56). HepCATT centres also had greater increases in HCV testing (OR = 3.06 versus 0.78, P < 0.001), referral to hepatology (OR = 9.60 versus 0.56, P < 0.001) and treatment initiation (OR = 9.5 versus 0.74, P < 0.001).

CONCLUSIONS

Introducing a half-time facilitator into drug and alcohol clinics in England increased engagement of HCV-positive people who inject drugs with hepatitis C virus care pathways, with increased uptake also of testing, referral to hepatology and initiation of treatment.

Monitoring the hepatitis C epidemic in England and evaluating intervention scale-up using routinely collected data

In England, 160 000 individuals were estimated to be chronically infected with hepatitis C virus (HCV) in 2005 and the burden of severe HCV-related liver disease has increased steadily for the past 15 years. Direct-acting antiviral treatments can clear infection in most patients, motivating HCV elimination targets. However, the current burden of HCV is unknown and new methods are required to monitor progress. We employed a Bayesian back-calculation approach, combining data on severe HCV-related liver disease and disease progression, to reconstruct historical HCV incidence and estimate current prevalence in England. We explicitly modelled infections occurring in people who inject drugs, the key risk group, allowing information on the size of this population and surveillance data on HCV prevalence to inform recent incidence. We estimated that there were 143 000 chronic infections in 2015 (95% credible interval 123 000-161 000), with 34% and 54% in those with recent and past injecting drug use, respectively. Following the planned scale-up of new treatments, chronic infections were predicted to fall to 113 400 (94 900-132 400) by the end of 2018 and to 89 500 (71 300-108 600) by the end of 2020. Numbers developing severe HCV-related liver disease were predicted to fall by at least 24% from 2015 to 2020. Thus, we describe a coherent framework to monitor progress using routinely collected data, which can be extended to incorporate additional data sources. Planned treatment scale-up is likely to achieve 2020 WHO targets for HCV morbidity, but substantial efforts will be required to ensure that HCV testing and patient engagement are sufficiently high.

Public Health Considerations among People who Inject Drugs with HIV/HCV Co-Infection: A Review

Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) co-infection among persons who inject drugs (PWID) is a major public health concern. There are limited data in clinical trials on the use of direct-acting antiviral (DAA) therapy for treatment of HCV in co-infected PWID. It is critical for these patients to gain access to treatment in order to decrease progression of liver disease and decrease transmission of both HIV and HCV. Additional harm reduction interventions, including needle and syringe programs and opioid substitution treatment, should be made available to this vulnerable population. Despite the importance of DAA treatment, the cost of DAA therapy and access to medical care is still a barrier to appropriate therapy. The purpose of this review is to present available data on the use of DAAs in co-infected PWID, review guideline recommendations for treatment and retreatment of HCV in co-infected PWID, provide cost considerations for DAA therapy, and provide recommendations about caring for patients who continue to inject drugs.

A dynamic Bayesian Markov model for health economic evaluations of interventions in infectious disease

BACKGROUND

Health economic evaluations of interventions in infectious disease are commonly based on the predictions of ordinary differential equation (ODE) systems or Markov models (MMs). Standard MMs are static, whereas ODE systems are usually dynamic and account for herd immunity which is crucial to prevent overestimation of infection prevalence. Complex ODE systems including distributions on model parameters are computationally intensive. Thus, mainly ODE-based models including fixed parameter values are presented in the literature. These do not account for parameter uncertainty. As a consequence, probabilistic sensitivity analysis (PSA), a crucial component of health economic evaluations, cannot be conducted straightforwardly.

METHODS

We present a dynamic MM under a Bayesian framework. We extend a static MM by incorporating the force of infection into the state allocation algorithm. The corresponding output is based on dynamic changes in prevalence and thus accounts for herd immunity. In contrast to deterministic ODE-based models, PSA can be conducted straightforwardly. We introduce a case study of a fictional sexually transmitted infection and compare our dynamic Bayesian MM to a deterministic and a Bayesian ODE system. The models are calibrated to simulated time series data.

RESULTS

By means of the case study, we show that our methodology produces outcome which is comparable to the "gold standard" of the Bayesian ODE system.

CONCLUSIONS

In contrast to ODE systems in the literature, the dynamic MM includes distributions on all model parameters at manageable computational effort (including calibration). The run time of the Bayesian ODE system is 15 times longer.

The Mexican consensus on the treatment of hepatitis C

The aim of the Mexican Consensus on the Treatment of HepatitisC was to develop clinical practice guidelines applicable to Mexico. The expert opinion of specialists in the following areas was taken into account: gastroenterology, infectious diseases, and hepatology. A search of the medical literature was carried out on the MEDLINE, EMBASE, and CENTRAL databases through keywords related to hepatitisC treatment. The quality of evidence was subsequently evaluated using the GRADE system and the consensus statements were formulated. The statements were then voted upon, using the modified Delphi system, and reviewed and corrected by a panel of 34 voting participants. Finally, the level of agreement was classified for each statement. The present guidelines provide recommendations with an emphasis on the new direct-acting antivirals, to facilitate their use in clinical practice. Each case must be individualized according to the comorbidities involved and patient management must always be multidisciplinary.

A Bayesian evidence synthesis approach to estimate disease prevalence in hard-to-reach populations: hepatitis C in New York City

Existing methods to estimate the prevalence of chronic hepatitis C (HCV) in New York City (NYC) are limited in scope and fail to assess hard-to-reach subpopulations with highest risk such as injecting drug users (IDUs). To address these limitations, we employ a Bayesian multi-parameter evidence synthesis model to systematically combine multiple sources of data, account for bias in certain data sources, and provide unbiased HCV prevalence estimates with associated uncertainty. Our approach improves on previous estimates by explicitly accounting for injecting drug use and including data from high-risk subpopulations such as the incarcerated, and is more inclusive, utilizing ten NYC data sources. In addition, we derive two new equations to allow age at first injecting drug use data for former and current IDUs to be incorporated into the Bayesian evidence synthesis, a first for this type of model. Our estimated overall HCV prevalence as of 2012 among NYC adults aged 20-59 years is 2.78% (95% CI 2.61-2.94%), which represents between 124,900 and 140,000 chronic HCV cases. These estimates suggest that HCV prevalence in NYC is higher than previously indicated from household surveys (2.2%) and the surveillance system (2.37%), and that HCV transmission is increasing among young injecting adults in NYC. An ancillary benefit from our results is an estimate of current IDUs aged 20-59 in NYC: 0.58% or 27,600 individuals.

Importance and Contribution of Community, Social, and Healthcare Risk Factors for Hepatitis C Infection in Pakistan

Pakistan has a high prevalence of hepatitis C virus (HCV) infection, estimated at 4.9% (2,290/46,843) in the 2007 national HCV seroprevalence survey. We used data from this survey to assess the importance of risk factor associations with HCV prevalence in Pakistan. Exposures were grouped as community (going to the barbers, sharing smoking equipment, having an ear/nose piercing, tattoo, or acupuncture), healthcare (ever having hemodialysis, blood transfusion, or ≥ 5 injections in the last year), demographic (marital status and age), and socio-economic (illiterate or laborer). We used mutually adjusted multivariable regression analysis, stratified by sex, to determine associations with HCV infection, their population attributable fraction, and how risk of infection accumulates with multiple exposures. Strength of associations was assessed using adjusted odds ratios (aOR). Community [aOR females 1.5 (95% confidence interval [CI]: 1.2, 1.8); males 1.2 (1.1, 1.4)] and healthcare [females 1.4 (1.2, 1.6); males 1.2 (1.1, 1.4)] exposures, low socio-economic status [females 1.6 (1.3, 1.80); males 1.3 (1.2, 1.5)], and marriage [females 1.5 (1.2, 1.9); males 1.4 (1.1, 1.8)] were associated with increased HCV infection. Among married women, the number of children was associated with an increase in HCV infection; linear trend aOR per child 1.06 (1.01, 1.11). Fewer infections could be attributed to healthcare exposures (females 13%; males 6%) than to community exposures (females 25%; males 9%). Prevalence increased from 3% to 10% when cumulative exposures increased from 1 to ≥ 4 [aOR per additional exposure for females 1.5 (1.4, 1.6); males 1.2 (1.2, 1.3)]. A combination of community, healthcare, and other factors appear to drive the Pakistan HCV epidemic, highlighting the need for a comprehensive array of prevention strategies.

Community nurse-led initiation of antiviral therapy for chronic hepatitis C in people who inject drugs does not increase uptake of or adherence to treatment

BACKGROUND

Chronic hepatitis C is common in people who inject drugs (PWID) and this population serves as a reservoir for infection. Treatment levels are low among this group, ranging from 1 to 19%. We explored whether a nurse-initiated community treatment model increased uptake of and adherence to interferon-based therapies.

METHODS

This was a cluster randomized trial of nurse-initiated versus physician-initiated antiviral therapy with pegylated interferon and ribavirin for hepatitis C virus in community clinics (trial registration: ISRCTN07774040).

RESULTS

The proportion of participants initiating treatment during follow-up was 10% with nurse-initiated (6/62) and 9% with physician-initiated (6/76) therapy. Adherence was similar in both groups, with only one patient in each arm not adhering to therapy. There were no serious adverse events, but interferon-related side effects were common. Drug and alcohol use did not change during therapy.

CONCLUSION

Despite easy access to antiviral therapy, uptake of treatment was poor, with no significant difference between the groups. Nurse-led initiation of interferon-based antiviral therapy in PWID did not lead to increased uptake of, response to or adherence with treatment. Further service improvement is unlikely to increase the proportion of PWID undergoing antiviral therapy for hepatitis C virus and early adoption of interferon-free regimens may increase the proportion initiating and completing treatment.

Prioritization of HCV treatment in the direct-acting antiviral era: An economic evaluation

BACKGROUND & AIMS

We determined the optimal HCV treatment prioritization strategy for interferon-free (IFN-free) HCV direct-acting antivirals (DAAs) by disease stage and risk status incorporating treatment of people who inject drugs (PWID).

METHODS

A dynamic HCV transmission and progression model compared the cost-effectiveness of treating patients early vs. delaying until cirrhosis for patients with mild or moderate fibrosis, where PWID chronic HCV prevalence was 20, 40 or 60%. Treatment duration was 12weeks at £3300/wk, to achieve a 95% sustained viral response and was varied by genotype/stage in alternative scenarios. We estimated long-term health costs (in £UK=€1.3=$1.5) and outcomes as quality adjusted life-years (QALYs) gained using a £20,000 willingness to pay per QALY threshold. We ranked strategies with net monetary benefit (NMB); negative NMB implies delay treatment.

RESULTS

The most cost-effective group to treat were PWID with moderate fibrosis (mean NMB per early treatment £60,640/£23,968 at 20/40% chronic prevalence, respectively), followed by PWID with mild fibrosis (NMB £59,258 and £19,421, respectively) then ex-PWID/non-PWID with moderate fibrosis (NMB £9,404). Treatment of ex-PWID/non-PWID with mild fibrosis could be delayed (NMB -£3,650). In populations with 60% chronic HCV among PWID it was only cost-effective to prioritize DAAs to ex-PWID/non-PWID with moderate fibrosis. For every one PWID in the 20% chronic HCV setting, 2 new HCV infections were averted. One extra HCV-related death was averted per 13 people with moderate disease treated. Rankings were unchanged with reduced drug costs or varied sustained virological response/duration by genotype/fibrosis stage.

CONCLUSIONS

Treating PWID with moderate or mild HCV with IFN-free DAAs is cost-effective compared to delay until cirrhosis, except when chronic HCV prevalence and reinfection risk is very high.

Is increased hepatitis C virus case-finding combined with current or 8-week to 12-week direct-acting antiviral therapy cost-effective in UK prisons? A prevention benefit analysis

Prisoners have a high prevalence of hepatitis C virus (HCV), but case-finding may not have been cost-effective because treatment often exceeded average prison stay combined with a lack of continuity of care. We assessed the cost-effectiveness of increased HCV case-finding and treatment in UK prisons using short-course therapies. A dynamic HCV transmission model assesses the cost-effectiveness of doubling HCV case-finding (achieved through introducing opt-out HCV testing in UK pilot prisons) and increasing treatment in UK prisons compared to status quo voluntary risk-based testing (6% prison entrants/year), using currently recommended therapies (8-24 weeks) or interferon (IFN)-free direct-acting antivirals (DAAs; 8-12 weeks, 95% sustained virological response, £3300/week). Costs (British pounds, £) and health utilities (quality-adjusted life years) were used to calculate mean incremental cost-effectiveness ratios (ICERs). We assumed 56% referral and 2.5%/25% of referred people who inject drugs (PWID)/ex-PWID treated within 2 months of diagnosis in prison. PWID and ex-PWID or non-PWID are in prison an average 4 and 8 months, respectively. Doubling prison testing rates with existing treatments produces a mean ICER of £19,850/quality-adjusted life years gained compared to current testing/treatment and is 45% likely to be cost-effective under a £20,000 willingness-to-pay threshold. Switching to 8-week to 12-week IFN-free DAAs in prisons could increase cost-effectiveness (ICER £15,090/quality-adjusted life years gained). Excluding prevention benefit decreases cost-effectiveness. If >10% referred PWID are treated in prison (2.5% base case), either treatment could be highly cost-effective (ICER<£13,000). HCV case-finding and IFN-free DAAs could be highly cost-effective if DAA cost is 10% lower or with 8 weeks' duration.

CONCLUSIONS

Increased HCV testing in UK prisons (such as through opt-out testing) is borderline cost-effective compared to status quo voluntary risk-based testing under a £20,000 willingness to pay with current treatments but likely to be cost-effective if short-course IFN-free DAAs are used and could be highly cost-effective if PWID treatment rates were increased. (Hepatology 2016;63:1796-1808).

Problem drug use prevalence estimation revisited: heterogeneity in capture-recapture and the role of external evidence

BACKGROUND AND AIMS

Capture-recapture (CRC) analysis is recommended for estimating the prevalence of problem drug use or people who inject drugs (PWID). We aim to demonstrate how naive application of CRC can lead to highly misleading results, and to suggest how the problems might be overcome.

METHODS

We present a case study of estimating the prevalence of PWID in Bristol, UK, applying CRC to lists in contact with three services. We assess: (i) sensitivity of results to different versions of the dominant (treatment) list: specifically, to inclusion of non-incident cases and of those who were referred directly from one of the other services; (ii) the impact of accounting for a novel covariate, housing instability; and (iii) consistency of CRC estimates with drug-related mortality data. We then incorporate formally the drug-related mortality data and lower bounds for prevalence alongside the CRC into a single coherent model.

RESULTS

Five of 11 models fitted the full data equally well but generated widely varying prevalence estimates, from 2740 [95% confidence interval (CI) = 2670, 2840] to 6890 (95% CI = 3740, 17680). Results were highly sensitive to inclusion of non-incident cases, demonstrating the presence of considerable heterogeneity, and were sensitive to a lesser extent to inclusion of direct referrals. A reduced data set including only incident cases and excluding referrals could be fitted by simpler models, and led to much greater consistency in estimates. Accounting for housing stability improved model fit considerably more than did the standard covariates of age and gender. External data provided validation of results and aided model selection, generating a final estimate of the number of PWID in Bristol in 2011 of 2770 [95% credible interval (Cr-I) = 2570, 3110] or 0.9% (95% Cr-I = 0.9, 1.0%) of the population aged 15-64 years.

CONCLUSIONS

Steps can be taken to reduce bias in capture-recapture analysis, including: careful consideration of data sources, reduction of lists to less heterogeneous subsamples, use of covariates and formal incorporation of external data.

An evidence synthesis approach to estimating the incidence of symptomatic pertussis infection in the Netherlands, 2005-2011

BACKGROUND

Despite high vaccination coverage, infection with Bordetella pertussis is a current public health concern in the Netherlands and other European Union member states. Because surveillance data are subject to extensive under-ascertainment and under-reporting, incidence is difficult to determine. Our objective was to estimate the age-group specific incidence of symptomatic pertussis infection in the Netherlands over the period 2005-2011, using multi-parameter evidence synthesis.

METHODS

Age-specific seroconversion probabilities were estimated for 2007 using Netherlands population data stratified by age-group and cross-sectional population-wide serosurvey (PIENTER-2) data, with a sero-diagnostic cut-off of 125 EU/ml as a proxy for recent infection. Symptomatic probabilities were derived from a study of household contacts and from PIENTER-2. The annual number of symptomatic infected (SI) persons was estimated using evidence synthesis methods in a Bayesian framework, by combining the estimated incidence of infection with notification data and symptomatic probabilities.

RESULTS

An incidence rate of 128 SI cases per 10,000 population (95 % credible interval [CrI]: 110-150) was estimated for 2005, which decreased to 107 per 10,000 (95 % CrI: 91-126) for 2011. The degree of underestimation in statutory notified cases was age-dependent, ranging from 10-fold (10-19 years) to 69-fold (60+ years). The largest annual decreases in SI incidence rate over the study period were in the 1-4 and 5-9 years age-groups (24.3 %, 15.9 % per year, respectively).

CONCLUSIONS

By synthesising all available data, the incidence of symptomatic pertussis and the extent to which SI is underrepresented by notification data can be estimated. Such estimates are essential for disease burden computation and for informing public health priority-setting.

Hepatitis C virus treatment as prevention in people who inject drugs: testing the evidence

PURPOSE OF REVIEW

The majority of hepatitis C virus (HCV) infections in the United Kingdom and many developing countries were acquired through injecting. New clinical guidance suggests that HCV treatment should be offered to people with a transmission risk - such as people who inject drugs (PWID) - irrespective of severity of liver disease. We consider the strength of the evidence base and potential problems in evaluating HCV treatment as prevention among PWID.

RECENT FINDINGS

There is good theoretical evidence from dynamic models that HCV treatment for PWID could reduce HCV chronic prevalence and incidence among PWID. Economic evaluations from high-income settings have suggested HCV treatment for PWID is cost-effective, and that in many settings HCV treatment of PWID could be more cost-effective than treating those at an equivalent stage with no ongoing transmission risk. Epidemiological studies of older interferon treatments have suggested that PWID can achieve similar treatment outcomes to other patient groups treated for chronic HCV. Impact and cost-effectiveness of HCV treatment is driven by the potential 'prevention benefit' of treating PWID. Model projections suggest that more future infections, end stage liver disease, and HCV-related deaths will be averted than lost through reinfection of PWID treated successfully for HCV. However, there is to date no empirical evidence from trials or observational studies that test the model projections and 'prevention benefit' hypothesis. In part this is because of uncertainty in the evidence base but also there is unlikely to have been a change in HCV prevalence due to HCV treatment because PWID HCV treatment rates historically in most sites have been low, and any scale-up and switch to the new direct acting antiviral has not yet occurred. There are a number of key uncertainties in the data available on PWID that need to be improved and addressed to evaluate treatment as prevention. These include estimates of the prevalence of PWID, measurements of HCV chronic prevalence and incidence among PWID, and how to interpret reinfection rates as potential outcome measures.

SUMMARY

Eliminating HCV through scaling up treatment is a theoretical possibility. But empirical data are required to demonstrate that HCV treatment can reduce HCV transmission, which will require an improved evidence base and analytic framework for measuring PWID and HCV prevalence.

The hepatitis C virus epidemics in key populations (including people who inject drugs, prisoners and MSM): the use of direct-acting antivirals as treatment for prevention

PURPOSE OF REVIEW

The burden of hepatitis C virus (HCV) is high among people who inject drugs (PWID) and prisoners, and increasing among HIV-infected MSM, who are key populations for HCV transmission in high-income countries and may also play a role in many in low- and middle-income countries. There is an increasing interest in the use of HCV antiviral treatment for prevention in these populations.

RECENT FINDINGS

Numerous theoretical modelling studies have explored the potential impact of HCV treatment for prevention among PWID in a range of global settings, generally finding that modest and achievable levels of HCV treatment, especially with interferon-free direct-acting antiviral therapy (IFN-free DAAs), could substantially reduce HCV chronic prevalence among PWID within the next 10-20 years. In addition, modelling studies have shown HCV testing and treatment in prison (including prevention benefits) could be cost-effective if continuity of care is ensured, or HCV treatments are shortened with DAAs. Modelling work among HIV-infected MSM has shown that further HCV treatment scale-up is likely required despite high treatment rates in this population. However, no empirical studies have explored whether HCV treatment can reduce HCV prevalence and prevent onwards transmission among those at risk of transmission.

SUMMARY

HCV treatment for key populations such as PWID, prisoners and MSM could become an important HCV prevention intervention, especially in the IFN-free DAA era. However, there is an urgent need to test these hypotheses through empirical studies.

Estimating the number of people with hepatitis C virus who have ever injected drugs and have yet to be diagnosed: an evidence synthesis approach for Scotland

AIMS

To estimate the number of people who have ever injected drugs (defined here as PWID) living in Scotland in 2009 who have been infected with the hepatitis C virus (HCV) and to quantify and characterize the population remaining undiagnosed.

METHODS

Information from routine surveillance (n=22616) and survey data (n=2511) was combined using a multiparameter evidence synthesis approach to estimate the size of the PWID population, HCV antibody prevalence and the proportion of HCV antibody prevalent cases who have been diagnosed, in subgroups defined by recency of injecting (in the last year or not), age (15-34 and 35-64 years), gender and region of residence (Greater Glasgow and Clyde and the rest of Scotland).

RESULTS

HCV antibody-prevalence among PWID in Scotland during 2009 was estimated to be 57% [95% CI=52-61%], corresponding to 46657 [95% credible interval (CI)=33812-66803] prevalent cases. Of these, 27434 (95% CI=14636-47564) were undiagnosed, representing 59% [95% CI=43-71%] of prevalent cases. Among the undiagnosed, 83% (95% CI=75-89%) were PWID who had not injected in the last year and 71% (95% CI=58-85%) were aged 35-64 years.

CONCLUSIONS

The number of undiagnosed hepatitis C virus-infected cases in Scotland appears to be particularly high among those who have injected drugs more than 1 year ago and are more than 35 years old.

Hepatitis C virus seroprevalence in pregnant women delivering live-born infants in North Thames, England in 2012

To estimate HCV seroprevalence in subpopulations of women delivering live-born infants in the North Thames region in England in 2012, an unlinked anonymous (UA) cross-sectional survey of neonatal dried blood spot samples was conducted. Data were available from 31467 samples from live-born infants received by the North Thames screening laboratory. Thirty neonatal samples had HCV antibodies, corresponding to a maternal seroprevalence of 0·095% (95% confidence interval 0·067–0·136). Estimated HCV seroprevalences in women born in Eastern Europe, Southern Asia and the UK were 0·366%, 0·162% and 0·019%, respectively. For women born in Eastern Europe seroprevalence was highest in those aged around 27 years, while in women born in the UK and Asia-Pacific region, seroprevalence increased significantly with age. HCV seroprevalence in UK-born women whose infant's father was also UK-born was 0·016%. One of the 30 HCV-seropositive women was HIV-1 seropositive. Estimated HCV seroprevalence for women delivering live-born infants in North Thames in 2012 (0·095%) was significantly lower than that reported in an earlier UA survey in 1997–1998 (0·191%). Data indicate that the cohort of UK-born HCV-seropositive women is ageing and that, in this area of England, most perinatally HCV-exposed infants were born to women themselves born in Southern Asia or Eastern Europe.

Projections of the current and future disease burden of hepatitis C virus infection in Malaysia

Background

The prevalence of hepatitis C virus (HCV) infection in Malaysia has been estimated at 2.5% of the adult population. Our objective, satisfying one of the directives of the WHO Framework for Global Action on Viral Hepatitis, was to forecast the HCV disease burden in Malaysia using modelling methods.

Methods

An age-structured multi-state Markov model was developed to simulate the natural history of HCV infection. We tested three historical incidence scenarios that would give rise to the estimated prevalence in 2009, and calculated the incidence of cirrhosis, end-stage liver disease, and death, and disability-adjusted life-years (DALYs) under each scenario, to the year 2039. In the baseline scenario, current antiviral treatment levels were extended from 2014 to the end of the simulation period. To estimate the disease burden averted under current sustained virological response rates and treatment levels, the baseline scenario was compared to a counterfactual scenario in which no past or future treatment is assumed.

Results

In the baseline scenario, the projected disease burden for the year 2039 is 94,900 DALYs/year (95% credible interval (CrI): 77,100 to 124,500), with 2,002 (95% CrI: 1340 to 3040) and 540 (95% CrI: 251 to 1,030) individuals predicted to develop decompensated cirrhosis and hepatocellular carcinoma, respectively, in that year. Although current treatment practice is estimated to avert a cumulative total of 2,200 deaths from DC or HCC, a cumulative total of 63,900 HCV-related deaths is projected by 2039.

Conclusions

The HCV-related disease burden is already high and is forecast to rise steeply over the coming decades under current levels of antiviral treatment. Increased governmental resources to improve HCV screening and treatment rates and to reduce transmission are essential to address the high projected HCV disease burden in Malaysia.

Factors affecting repeated cessations of injecting drug use and relapses during the entire injecting career among the Edinburgh Addiction Cohort

BACKGROUND AND AIMS

Injecting drug use is a chronic condition, with people who inject drugs (PWID) typically experiencing repeated cessations and relapses during their injection careers. We characterize patterns of ceasing and relapsing and the impact of opiate substitution treatment (OST) during the entire injecting careers of PWID in the Edinburgh Addiction Cohort (EAC).

METHODS

During 2005-2007, 432 surviving participants of the EAC were interviewed about their injecting histories. Adjusted associations between covariates and hazards of cessation and relapse were estimated using random-effects models.

RESULTS

OST was strongly associated with a higher hazard of cessation (HR = 1 .71, P < 0.001), but there was no significant evidence of association with hazard of relapse (HR = 0.81, P = 0.14). Women and older PWID were less likely to relapse (HR = 0.73, P = 0.02 and HR = 0.55, P < 0.001, respectively). Hazards of both cessation and relapse decreased monotonically with time since last relapse/cessation (both P < 0.001). An individual's hazard of cessation increased with his/her number of previous cessations (HR = 3.58 for 10+ previous cessations, P < 0.001), but there was no evidence that an individual's hazard of relapse changed with number of previous relapses (P = 0.37). There was heterogeneity in the individual hazards of both cessation and relapse.

CONCLUSIONS

OST was associated with reduced time to cessation, and there was some suggestion of increased time to relapse too. The likelihood of prolonged cessation is greater for women, increases with age, and decreases with time since last relapse.

Case-finding for hepatitis C in primary care: a mixed-methods service evaluation

BACKGROUND

Hepatitis C is often asymptomatic, presenting with liver failure and cancer decades after infection. People who inject drugs (PWID) and immigrant populations from countries with a moderate-to-high prevalence of hepatitis C virus (HCV) are the main risk groups. Deaths and hospital admissions due to HCV cirrhosis tripled between 1998 and 2010, but the majority of people with chronic HCV are unaware of it.

AIM

To identify patients at risk of developing hepatitis C using routine GP data, to determine the proportion not tested, and to explore GPs' views regarding testing.

DESIGN AND SETTING

Mixed-methods service evaluation (density-based selection of PWID) in six NHS practices in Bristol.

METHOD

Patients at risk of HCV were identified. The Health Protection Agency laboratory (now part of Public Health England) provided test results. Semi-structured interviews with 17 GPs were audiorecorded and thematic analyses conducted on anonymised transcripts.

RESULTS

Of 3765 patients identified as being at risk of developing hepatitis C, 3051 (81%) had no test result, including 53% of PWID and 93% of the 'ethnicity' group. All GPs said they usually test PWID. Most GPs test for HIV and hepatitis B in immigrants more often than they test for HCV. Barriers to testing included not questioning patients about risk factors, competing priorities, the chaotic lifestyle of PWID, difficulty extracting information from computerised records, and forgetting to address HCV.

CONCLUSION

Computer prompts and GP education on whom to test are warranted. Ensuring that country of origin and drug use is included on the new-patient questionnaire might also aid case-finding for HCV.

HCV treatment rates and sustained viral response among people who inject drugs in seven UK sites: real world results and modelling of treatment impact

Hepatitis C virus (HCV) antiviral treatment for people who inject drugs (PWID) could prevent onwards transmission and reduce chronic prevalence. We assessed current PWID treatment rates in seven UK settings and projected the potential impact of current and scaled-up treatment on HCV chronic prevalence. Data on number of PWID treated and sustained viral response rates (SVR) were collected from seven UK settings: Bristol (37-48% HCV chronic prevalence among PWID), East London (37-48%), Manchester (48-56%), Nottingham (37-44%), Plymouth (30-37%), Dundee (20-27%) and North Wales (27-33%). A model of HCV transmission among PWID projected the 10-year impact of (i) current treatment rates and SVR (ii) scale-up with interferon-free direct acting antivirals (IFN-free DAAs) with 90% SVR. Treatment rates varied from <5 to over 25 per 1000 PWID. Pooled intention-to-treat SVR for PWID were 45% genotypes 1/4 [95%CI 33-57%] and 61% genotypes 2/3 [95%CI 47-76%]. Projections of chronic HCV prevalence among PWID after 10 years of current levels of treatment overlapped substantially with current HCV prevalence estimates. Scaling-up treatment to 26/1000 PWID annually (achieved already in two sites) with IFN-free DAAs could achieve an observable absolute reduction in HCV chronic prevalence of at least 15% among PWID in all sites and greater than a halving in chronic HCV in Plymouth, Dundee and North Wales within a decade. Current treatment rates among PWID are unlikely to achieve observable reductions in HCV chronic prevalence over the next 10 years. Achievable scale-up, however, could lead to substantial reductions in HCV chronic prevalence.

Hepatitis C virus infection and risk factors in the general population: a large community-based study in eastern China, 2011-2012

Limited information is available on the prevalence of hepatitis C virus (HCV) in the general population in China. A community-based epidemiological study was conducted in three counties in eastern China. A total of 149 175 individuals were investigated in 60 communities in three counties in Jiangsu province, eastern China, of whom 1175 subjects [0·79%, 95% confidence interval (CI) 0·74-0·83] were HCV antibody positive. The prevalence was low in children (0·09%, 95% CI 0·04-0·17), but increased progressively from adolescents (0·20%, 95% CI 0·15-0·28) to adults aged ⩾21 years (95% CI 0·15-1·64). Women had a higher prevalence of HCV infection than men in most age groups. In a multilevel regression analysis, age, sex, education, occupation, blood transfusion [odds ratio (OR) 2·91, 95% CI 1·09-5·37], invasive testing (OR 1·28, 95% CI 1·14-1·61), and dental therapy (OR 2·27, 95% CI 1·41-3·42) were associated with HCV infection. In conclusion, although the prevalence of HCV in this population was lower than reported from national levels, the total reservoir of infection is significant and warrants public health measures, such as health education to limit the magnitude of the problem.

Bridging the data gaps in the epidemiology of hepatitis C virus infection in Malaysia using multi-parameter evidence synthesis

BACKGROUND

Collecting adequate information on key epidemiological indicators is a prerequisite to informing a public health response to reduce the impact of hepatitis C virus (HCV) infection in Malaysia. Our goal was to overcome the acute data shortage typical of low/middle income countries using statistical modelling to estimate the national HCV prevalence and the distribution over transmission pathways as of the end of 2009.

METHODS

Multi-parameter evidence synthesis methods were applied to combine all available relevant data sources - both direct and indirect - that inform the epidemiological parameters of interest.

RESULTS

An estimated 454,000 (95% credible interval [CrI]: 392,000 to 535,000) HCV antibody-positive individuals were living in Malaysia in 2009; this represents 2.5% (95% CrI: 2.2-3.0%) of the population aged 15-64 years. Among males of Malay ethnicity, for 77% (95% CrI: 69-85%) the route of probable transmission was active or a previous history of injecting drugs. The corresponding proportions were smaller for male Chinese and Indian/other ethnic groups (40% and 71%, respectively). The estimated prevalence in females of all ethnicities was 1% (95% CrI: 0.6 to 1.4%); 92% (95% CrI: 88 to 95%) of infections were attributable to non-drug injecting routes of transmission.

CONCLUSIONS

The prevalent number of persons living with HCV infection in Malaysia is estimated to be very high. Low/middle income countries often lack a comprehensive evidence base; however, evidence synthesis methods can assist in filling the data gaps required for the development of effective policy to address the future public health and economic burden due to HCV.

Combination interventions to prevent HCV transmission among people who inject drugs: modeling the impact of antiviral treatment, needle and syringe programs, and opiate substitution therapy

BACKGROUND

Interventions such as opiate substitution therapy (OST) and high-coverage needle and syringe programs (HCNSP) cannot substantially reduce hepatitis C virus (HCV) prevalence among people who inject drugs (PWID). HCV antiviral treatment may prevent onward transmission. We project the impact of combining OST, HCNSP, and antiviral treatment on HCV prevalence/incidence among PWID.

METHODS

An HCV transmission model among PWID was used to project the combinations of OST, HCNSP, and antiviral treatment required to achieve different prevalence and incidence reductions within 10 years for 3 chronic prevalence scenarios and the impact of HCV treatment if only delivered through OST programs. Multivariate and univariate sensitivity analyses were performed.

RESULTS

Large reductions (>45%) in HCV chronic prevalence over 10 years require HCV antiviral treatment. Scaling up OST and HCNSP substantially reduces the treatment rate required to achieve specific HCV prevalence reductions. If OST and HCNSP coverage were increased to 40% each (no coverage at baseline), then annually treating 10, 23, or 42 per 1000 PWID over 10 years would halve prevalence for 20%, 40%, or 60% baseline chronic HCV prevalences, respectively. Approximately 30% fewer treatments are necessary with new direct-acting antivirals. If coverage of OST and HCNSP is 50% at baseline, similar prevalence reductions require higher treatment rates for the same OST and HCNSP coverage.

CONCLUSIONS

Combining antiviral treatment with OST with HCNSP is critical for achieving substantial reductions (>50%) in HCV chronic prevalence over 10 years. Empirical studies are required on how best to scale up antiviral treatment and combine treatment with other interventions.

Hepatitis C avoidance in injection drug users: a typology of possible protective practices

Introduction

Hepatitis C virus (HCV) represents a serious public health concern. People who inject drugs (PWID) are at particular risk and nearly half (45%) of PWID in England may be infected. HCV prevention interventions have only had moderate impact on the prevalence of HCV in this population. Using qualitative methods, we sought to detail the protective practices potentially linked to HCV avoidance among PWID, and explore the motivations for these.

Methods

The study used a life history approach allowing participants to detail their lived experience both before and during the course of their injecting careers. Thirty-seven participants were recruited from drug services in London, and from referrals within local injecting networks. A baseline and follow-up in-depth qualitative interview was carried out with each participant, and for half, a third interview was also undertaken. All underwent testing for HCV antibody. Analyses focused on developing a descriptive typology of protective practices potentially linked to HCV avoidance.

Results

Practices were deemed to be protective against HCV if they could be expected a priori to reduce the number of overall injections and/or the number of injections using shared injecting equipment. Participants reported engaging in various protective practices which fell into three categories identified through thematic analysis: principles about injecting, preparedness, and flexibility.

Conclusions

All participants engaged in protective practices irrespective of serostatus. It is important to consider the relative importance of different motivations framing protective practices in order to formulate harm reduction interventions which appeal to the situated concerns of PWID, especially given that these protective practices may also help protect against HIV and other blood borne infections.

Combination therapy of natural human interferon-beta and ribavirin for chronic hepatitis C patients with injection drug use

AIM

The aim of this study was to evaluate the efficacy and safety of combination therapy using natural human interferon-β and ribavirin (IFN-β/RBV) for chronic hepatitis C patients who were injection drug users (IDU) and resident in the Airin district of Osaka, containing the biggest slums in Japan.

METHODS

Twenty-nine IDU with chronic hepatitis C received combination therapy of IFN-β/RBV. The psychiatrist in charge evaluated the scores of the Zung Self-rating Depression Scale (SDS), a self-rating scale based on 20 questions. Univariate logistic regression analyses were used to determine the factors that significantly contributed to complete treatment and a sustained virological response (SVR).

RESULTS

Thirteen of the 29 patients achieved SVR according to the intention to treat analysis. All patients with a rapid virological response achieved SVR. No patient required a reduced dose of RBV because of a decrease in their hemoglobin level, or of IFN-β because of a low level of white blood cells and platelet count. Two patients had psychological side-effects and stopped the therapy early in the treatment; one patient had depression and the other had anxious depression. Univariate logistic regression analyses indicated that the stage of fibrosis was the only factor that contributed to SVR, and that the SDS test and past drug abuse contributed to completion of the treatment.

CONCLUSION

IFN-β/RBV combination therapy is useful for treating IDU.

Multiple parameter evidence synthesis--a potential solution for when information on drug use and harm is in conflict

The quality of the evidence on estimating drug-related harm is not yet as advanced as that for intervention effectiveness. Multiple parameter evidence synthesis offers a potential solution, in which 'all available evidence' is combined into a single coherent model.We present a case study of estimating the number of people infected with hepatitis C.

Estimating the prevalence of hepatitis C infection in New York City using surveillance data

Hepatitis C virus is the most common chronic blood-borne infection in the USA. Based on results of a serosurvey, national prevalence is estimated to be 1·3% or 3·2 million people. Sub-national estimates are not available for most jurisdictions. Hepatitis C surveillance data was adjusted for death, out-migration, under-diagnosis, and undetectable blood RNA, to estimate prevalence in New York City (NYC). The prevalence of hepatitis C infection in adults aged ⩾20 years in NYC is 2·37% (range 1·53–4·90%) or 146 500 cases of hepatitis C. This analysis presents a mechanism for generating prevalence estimates using local surveillance data accounting for biases and difficulty in accessing hard to reach populations. As the cohort of patients with hepatitis C age and require additional medical care, local public health officials will need a method to generate prevalence estimates to allocate resources. This approach can serve as a guideline for generating local estimates using surveillance data that is less resource prohibitive.

Respondent driven sampling and community structure in a population of injecting drug users, Bristol, UK

BACKGROUND

A 2006 respondent driven sampling (RDS) survey of injecting drug users (IDUs) in Bristol, UK, estimated 40 per 100 person years HCV incidence but in 2009 another RDS survey estimated only 10 per 100 person years incidence amongst the same population. Estimated increases in intervention exposure do not fully explain the decrease in risk. We investigate whether the underlying contact network structure and differences in the structure of the RDS trees could have contributed to the apparent change in incidence.

METHOD

We analyse the samples for evidence that individuals recruit participants who are like themselves (assortative recruiting). Using an assortativity measure, we develop a Monte Carlo approach to determine whether the RDS data exhibit significantly more assortativity than is expected for that sample. Motivated by these findings, a network model is used to investigate how much assortativity and the structure of the RDS tree impacts sample estimates of prevalence and incidence.

RESULTS

The samples suggest there is some assortativity on injecting habits or markers of injecting risk. The 2009 sample has lower assortativity than 2006. Simulations of RDS confirm that assortativity influences the estimated incidence in a population and the structure of RDS samples can result in bias. Our simulations suggest that RDS incidence estimates have considerable variance, making them difficult to use for monitoring trends.

CONCLUSIONS

We suggest there was likely to have been a decline in risk between 2006 and 2009 due to increased intervention coverage, but the bias and variance in the estimates prevents accurate estimation of the incidence.

Can needle and syringe programmes and opiate substitution therapy achieve substantial reductions in hepatitis C virus prevalence? Model projections for different epidemic settings

AIMS

To investigate the impact of scaling-up opiate substitution therapy (OST) and high coverage needle and syringe programmes (100%NSP-obtaining more sterile syringes than you inject) on HCV prevalence among injecting drug users (IDUs).

DESIGN

Hepatitis C virus HCV transmission modelling using U.K. estimates for effect of OST and 100%NSP on individual risk of HCV infection.

SETTING

Range of chronic HCV prevalent (20/40/60%) settings with no OST/100%NSP, and U.K. setting with 50% coverage of both OST and 100%NSP.

PARTICIPANTS

Injecting drug users.

MEASUREMENTS

Decrease in HCV prevalence after 5-20 years due to scale-up of OST and 100%NSP to 20/40/60% coverage in no OST/100%NSP settings, or from 50% to 60/70/80% coverage in the U.K. setting.

FINDINGS

For 40% chronic HCV prevalence, scaling-up OST and 100%NSP from 0% to 20% coverage reduces HCV prevalence by 13% after 10 years. This increases to a 24/33% relative reduction at 40/60% coverage. Marginally less impact occurs in higher prevalence settings over 10 years, but this becomes more pronounced over time. In the United Kingdom, without current coverage levels of OST and 100%NSP the chronic HCV prevalence could be 65% instead of 40%. However, increasing OST and 100%NSP coverage further is unlikely to reduce chronic prevalence to less than 30% over 10 years unless coverage becomes ≥80%.

CONCLUSIONS

Scaling-up opiate substitution therapy and high coverage needle and syringe programmes can reduce hepatitis C prevalence among injecting drug users, but reductions can be modest and require long-term sustained intervention coverage. In high coverage settings, other interventions are needed to further decrease hepatitis C prevalence. In low coverage settings, sustained scale-up of both interventions is needed.

Hepatitis C virus prevalence in The Netherlands: migrants account for most infections

A population-based anti-hepatitis C virus (HCV) prevalence is important for surveillance purposes and it provides insight into the burden of disease. The outcomes of recent studies in the general Dutch population as well as recent HCV data from specific risk groups including migrants, men who have sex with men (MSM) and injecting drug users (IDUs), were implemented in a modified version of the Workbook Method (a spreadsheet originally designed for HIV estimations), to estimate Dutch HCV seroprevalence. The estimated national seroprevalence of HCV was 0·22% (min 0·07%, max 0·37%), corresponding to 28 100 (min n = 9600, max n = 48 000) HCV-infected individuals in The Netherlands. Of these, first-generation migrants from HCV-endemic countries (HCV prevalence ≥2%) accounted for the largest HCV-infected group, followed by IDUs and HIV-positive MSM.

Hepatitis C prevalence in Denmark -an estimate based on multiple national registers

BACKGROUND

A national survey for chronic hepatitis C has not been performed in Denmark and the prevalence is unknown. Our aim was to estimate the prevalence of chronic hepatitis C from public registers and the proportion of these patients who received specialized healthcare.

METHODS

Patients with a diagnosis of chronic hepatitis C were identified from four national registers: a laboratory register, the Hospital Discharge Register, a clinical database of chronic viral hepatitis and the Register of Communicable Diseases. The total population diagnosed with hepatitis C was estimated by capture-recapture analysis. The population with undiagnosed hepatitis C was derived from the national register of drug users by comparing diagnosed and tested persons.

RESULTS

A total of 6,935 patients diagnosed with chronic hepatitis C were identified in the four registers and the estimated population diagnosed with the disease was 9,166 persons (95% C.I. interval 8,973 - 9,877), corresponding to 0.21% (95% CI 0.21%-0.23%) of the Danish population over 15 years of age. The prevalence was highest among persons 40-49 years old (0.39%) and males (0.28%). It was estimated that 40% of the diagnosed patients lived in the capital region, and 33.5% had attended specialised healthcare. It was estimated that 46% of hepatitis C patients had not been diagnosed and the total population with chronic hepatitis C in Denmark was 16,888 (95% C.I. 16,474-18,287), corresponding to 0.38% (95% CI 0.37-0.42) of the population over 15 years of age.

CONCLUSIONS

The estimated prevalence of chronic hepatitis C in Denmark was 0.38%. Less than half of the patients with chronic hepatitis C in Denmark have been identified and among these patients, one in three has attended specialised care.

Hepatitis C infection among recent initiates to injecting in England 2000-2008: Is a national hepatitis C action plan making a difference?

Around 80% of hepatitis C virus (HCV) infections in England are among injecting drug users (IDUs). The HCV Action Plan launched in 2004 includes targets to reduce HCV prevalence in recent initiates (those starting injecting in the preceding 3 years), and to increase HCV voluntary confidential testing (VCT). The Action Plan's impact is examined using surveillance data from recent initiates participating in an annual survey of IDUs in contact with specialist services across England, 2000-2008. Participants provided an oral fluid sample (tested for anti-HCV) and completed a short questionnaire (including HCV VCT and result of last test). Overall, anti-HCV prevalence among the recent initiates was 18% (619/3463); in 2004, it was 20% (59/291), other than being lower in 2000 [11%, 73/672, adjusted odds ratio (AOR) = 0.63 95%CI 0.42-0.93] there was no change over time. Prevalence increased with age; was higher among those ever imprisoned, using a needle exchange, and having a HCV VCT; and varied by region. Overall, 42% (1460) had ever had a HCV VCT; in 2004 uptake was 45% (130/291) having increased from 26% (175/672, AOR = 0.57 95%CI 0.42-0.77) in 2000, and it rose to 62% (197/320, AOR = 2.12 95%CI 1.50-2.99) in 2008. The proportion of anti-HCV-positive IDUs aware of their infection was higher in 2006-2008 than in earlier years. The HCV Action Plan has probably helped increase recent initiates' uptake of HCV VCT and the proportion of those diagnosed with HCV infection. However, its impact on HCV transmission is unclear. There is a need to reinvigorate, and improve coverage of, interventions to prevent HCV transmission.

Cost-effectiveness of hepatitis C virus antiviral treatment for injection drug user populations

Injecting drug use is the main risk of hepatitis C virus (HCV) transmission in most developed countries. HCV antiviral treatment (peginterferon-α + ribavirin) has been shown to be cost-effective for patients with no reinfection risk. We examined the cost-effectiveness of providing antiviral treatment for injecting drug users (IDUs) as compared with treating ex/non-IDUs or no treatment. A dynamic model of HCV transmission and disease progression was developed, incorporating: a fixed number of antiviral treatments allocated at the mild HCV stage over 10 years, no retreatment after treatment failure, potential reinfection, and three baseline IDU HCV chronic prevalence scenarios (20%, 40%, and 60%). We performed a probabilistic cost-utility analysis estimating long-term costs and outcomes measured in quality adjusted life years (QALYs) and calculating the incremental cost-effectiveness ratio (ICER) comparing treating IDUs, ex/non-IDUs, or no treatment. Antiviral treatment for IDUs is the most cost-effective option in the 20% and 40% baseline chronic prevalence settings, with ICERs compared with no treatment of £ 521 and £ 2,539 per QALY saved, respectively. Treatment of ex/non-IDUs is dominated in these scenarios. At 60% baseline prevalence, treating ex/non-IDUs is slightly more likely to be the more cost-effective option (with an ICER compared with no treatment of £ 6,803), and treating IDUs dominated due to high reinfection. A sensitivity analysis indicates these rankings hold even when IDU sustained viral response rates as compared with ex/non-IDUs are halved.

CONCLUSION

Despite the possibility of reinfection, the model suggests providing antiviral treatment to IDUs is the most cost-effective policy option in chronic prevalence scenarios less than 60%. Further research on how HCV treatment for injectors can be scaled up and its impact on prevalence is warranted.