BMJ Open 2012;2:e001637 doi:10.1136/bmjopen-2012-001637
Estimation of cocaine consumption in the community: a critical comparison of the results from three complimentary techniques
Malcolm J Reid, Katherine H Langford, Merete Grung, Hallvard Gjerde, Ellen J Amundsen, Jorg Morland, Kevin V Thomas
Cocaine is the most commonly used illicit stimulant drug in Europe and consumption remains high in the USA despite a recent decline in annual prevalence.1 Use of the drug is associated with numerous health problems including cardiovascular disorders, neurological impairment and death.2 Accurate and timely information on the prevalence of cocaine use are therefore important for assessing the needs of public health, developing appropriate drug strategies to reduce health effects and in the subsequent monitoring of the effectiveness of such strategies.
While official statistics indicate that cocaine use is relatively stable in Europe and may be dropping in the USA, it is generally accepted that there is a lack of information with respect to the dynamics and scale of illicit drug markets, and the validity or reliability of estimates are questionable.3 The estimation of drug use patterns in society is currently reliant on questionnaire-based data collection at the population level, and among groups of drug users, together with statistics from hospital admissions, registered drug-overdose deaths, treatment services and the records from police seizures.4–8 Validation of drug-use statistics derived from individual self-reporting has previously been attempted by drawing comparisons between the self-reported use and measurements of samples taken from hair, urine and blood.9–13 This technique has shown that despite the use of an array of methods to increase the level of accuracy of self-reporting, under-reporting is still apparent. Recently, additional data on the level of drug use at the community level have also been acquired through the implementation of anonymous road-side testing studies,14 ,15 and also through the measurement of drug metabolites in sewage water.16–21 With a range of different approaches now available to estimate the level of community drug use it is highly desirable to critically compare the results they provide. For the first time this paper presents a critical comparison of the results from three different methods for estimating the level of cocaine use in the general population. The comparison was performed on three studies in Oslo, Norway and applies to; a combination of user group and representative population sample survey questionnaires, a representative sample survey on drug use measured in saliva among drivers, and an analysis of the quantity of drugs and drug-related metabolites in sewage.