Estimating the prevalence of problem drug use

Speaker: Dr Gordon Hay (Centre for Drug Misuse Research, University of Glasgow)

Abstract

Household surveys have typically been considered inappropriate to estimate the prevalence of problem drug use, such as the use of opiates such as heroin. The capture-recapture method, which was originally developed to estimate the size of animal populations, has been used in various settings across Europe to estimate the size of drug using populations. The capture-recapture method combines data from three or more sources, such as drug treatment agencies and the police and fits a log-linear model to the aggregated overlap data. To obtain the overlap pattern, the method requires individual-based data and therefore can involve substantial data collection. Another method, known as the multiple indicator model, can also be used to estimate the prevalence of drug use where it is not possible to use the capture-recapture method.

In a Home Office funded study in England, estimates of the prevalence of opiate and / or crack cocaine use in all 149 local areas were derived using either the capture-recapture method or a multiple indicator model. In this presentation I will discuss this study, in particular the approach taken in model selection and deriving confidence intervals.