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BMJ No 7108 Volume 315 Papers Saturday 6 September 1997
Validation of a regional drug misuse database: implications for policy and surveillance of problem drug use in the UKMatthew Hickman, Heather Sutcliffe, Arun Sondhi, Gerry V Stimson See Editorial by Farrell p 559, Letters p 601, Personal view p 613 The eight regional drug misuse databases constitute the largest investment (about £100,000 each annually) in drugs surveillance in England. Along with databases in Scotland and Wales, they provide the main intelligence on problem drug takers, including monitoring government targets.(1) They were established because of the lack of information on clients of drug agencies(2) but have attracted criticism for not properly informing policymakers of the extent of drug use and not accurately assessing client volume.(3) We performed a study in North Thames to assess the level of underreporting of "episodes" (new clients or clients who reattend after an absence of six months(4)) to the regional database and the relation between episodes and the number of clients and prevalent drug takers attending agencies in a year. Methods and resultsOver 80% of reports to the North Thames database come from 62 specialist drug agencies. These were categorised according to type, and a sample selected using random number tables: 3 from 8 drug dependency units, 9 from 27 statutory community based drug services, 5 from 16 non-statutory community services, 2 from 9 residential rehabilitation units, and 1 of 2 needle exchanges. Two statutory community services refused and were not replaced. A further six agencies which did not participate in the database were identified. Two were selected randomly (both non-statutory community services) and agreed to participate, making a final sample of 20 agencies (29%). A researcher visited the agencies (April-December 1995) to collect a standard dataset on everyone who attended during 1994. These were matched with individual agency reports for 1994 and then against the whole dataset in the database using initials, date of birth, sex, and, in uncertain matches, postcode, ethnic group, drug problem, and date of report. Altogether 5,673 clients, 4,543 episodes, and 5,136 prevalent problem drug takers were collected from the 20 agencies. There were fewer episodes and drug takers than clients because only new clients and those who reattend after a six month gap generate a new episode and drug takers may attend more than one agency. The table summarises the under-reporting. The level of reporting differed by type of agency: 9% of episodes at drug dependency units were unreported compared with 20% for non-statutory community services, 31% for statutory community services, 40% for residential rehabilitation units, and 63% for the needle exchange. About half the 40% shortfall between database reports and agency records of clients (excluding the two agencies which did not report) was due to under-reporting (998) with the remainder due to the "episode" definition excluding continuing clients who have not had six months between attendances (1037).
CommentThis study is the first to assess systematically the coverage and validity of the drug misuse database. Our estimates, generalisable to North Thames, also represent the best available for adjusting national figures. Though an earlier study estimated underreporting at less than 3%, the sample was self selected from agencies with the largest number of reports and biased towards high levels of reporting.(5) Most specialist drug agencies in North Thames participate in the regional database, and in terms of coverage (including completeness of reporting) it compares favourably with other surveillance systems in the UK. Nevertheless, the database does not measure the prevalence of known problem drug takers, which means it is inadequate for planning services and provides a false picture of trends of visible drug use. The database needs to be changed rather than abandoned since policymakers and health services need information on drug users in contact with services.
We thank staff of the agencies who participated in this
exercise.
Funding: North Thames Regional Health Authority. The Centre for
Research on Drugs and Health Behaviour is core funded by the research
and development directorate of North Thames regional office of NHS
Executive.
(Accepted 8 April 1997) Centre for Research on Drugs and Health
Behaviour, Correspondence to: Mr Hickman References 1 Tackling drugs together. A strategy for England 1995-1998. HMSO: London, 1995. 2 Stimson G V. AIDS and injecting drug use in the United Kingdom, 1987-1993: the policy response and the prevention of the epidemic. Soc Sci Med 1995; 41:699-716. 3 Sutton M, Maynard M. Are drug policies based on fake statistics? Addiction 1993; 88:455-8. 4 Donmall M C. The drug misuse database: local monitoring of presenting drug use. London: Department of Health 1990. 5 Crabbe T. Drug workers and the drug misuse database. International Journal of Drug Policy 1995;6:31-8.
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