Estimating the prevalence of problem drug use from drug-related mortality data
Open Access
- 8 June 2020
- Vol. 115 (12), 2393-2404
- https://doi.org/10.1111/add.15111
Abstract
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.Funding Information
- Medical Research Council (G1000021, MR/M014533/1)
- National Institute for Health Research (HPRU in Evaluation of Interventions)
This publication has 54 references indexed in Scilit:
- Trends in the Population Prevalence of People Who Inject Drugs in US Metropolitan Areas 1992–2007PLOS ONE, 2013
- Mortality among people who inject drugs: a systematic review and meta-analysisBulletin of the World Health Organization, 2013
- Mortality of those who attended drug services in Scotland 1996–2006: Record-linkage studyInternational Journal of Drug Policy, 2012
- Insights into the rise in HIV infections, 2001 to 2008: a Bayesian synthesis of prevalence evidenceAIDS, 2010
- Counting hard-to-count populations: the network scale-up method for public healthSexually Transmitted Infections, 2010
- Estimating current injectors in Scotland and their drug-related death rate by sex, region and age-group via Bayesian capture—recapture methodsStatistical Methods in Medical Research, 2008
- Estimating the Prevalence of Injection Drug Users in the U.S. and in Large U.S. Metropolitan Areas from 1992 to 2002Journal of Urban Health, 2008
- Bayesian Measures of Model Complexity and FitJournal of the Royal Statistical Society Series B: Statistical Methodology, 2002
- DiscussionJournal of Clinical Epidemiology, 1999
- A Method for Obtaining Short-Term Projections and Lower Bounds on the Size of the AIDS EpidemicJournal of the American Statistical Association, 1988