estimation of the prevalence of problem drug use in lithuania
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Estimation of the Prevalence of Problem Drug Use in
Lithuania Dr Gordon Hay
Centre for Drug Misuse ResearchUniversity of Glasgow, United
Kingdom
Introduction
• Background• Definition• Methods to Estimate Prevalence
– Mortality Multiplier– Capture-recapture Methods– truncated Poisson method
• Prevalence Estimates– Vilnius, Klaipeda & Lithuania
• Discussion
Background
• UNODC project– Project “HIV/AIDS prevention and care among
injecting drug users and in prison settings in Estonia, Latvia and Lithuania”
• Objectives– To obtain estimates of Problem Drug Use
(PDU) and Injecting Drug Use (IDU) prevalence
• 5 days fieldwork (September 2007)• Workshop on prevalence estimation
My experience
• United Kingdom Government– Estimating the prevalence of problem drug
use• Dundee (1994)• Lanarkshire (2007), Aberdeen (1998)• Scotland (2000, 2003, 2006)• England (2004, 2005, 2006)• Northern Ireland (2005)
– Other studies• Cohort study of drug users in treatment• Children / young people
My Experience
• European Monitoring Centre for Drugs and Drug Addiction (EMCDDA)– All member states required to provide
information on the prevalence of problem drug use
• Seven Cities Study (1997)– Dublin, Helsinki, Rome, Rotterdam, Setubal
Toulouse & Vienna
• Methodological Studies• UK Scientific Expert (problem drug use)
My Experience
• Synergy project– USAID / Family Health International projects– Prevalence estimation in Estonia, Latvia and
Lithuania• Fieldwork in Klaipeda, Riga, Tallinn & Vilnius
– Prevalence estimate for Riga– Recommendations
– Involved in prevalence estimation study in Tallinn
Definitions
• EMCDDA defines problem drug use as:– injecting drug use or long-duration / regular use of
opiates, cocaine and / or amphetamines
• In this study / estimation we define problem drug use as:– Opiate use (mostly opiate injecting)
– We do not include stimulant or marijuana use
Methods to Estimate Prevalence• Indirect methods
– Mortality Multiplier Method– Capture-recapture Method– truncated Poisson Method– Multiple Indicator Method
• Estimate the size of hidden populations
General Idea
• There are some problem drug users that are ‘visible’ or ‘identifiable’ or ‘known’– Treatment– Police– Mortality
• A proportion of problem drug users are visible– In United Kingdom about 40 – 50% in treatment
• Data on visible population can be used to estimate the size of the total population
Mortality Multiplier
• Uses the:– Number of drug-related deaths– Mortality rate
• Both need to refer to the same population, such as opiate users
Drug related death dataSource: Health Statistics Quarterly
Number of deaths related to drug misuse
0
200
400
600
800
1000
1200
1400
1600
1800
2000 2001 2002 2003 2004 2005
Females
Males
1,506 deaths in 2005
Mortality Multiplier
• 1,506 drug-related deaths in 2005• What is the mortality rate?
– Anecdotal evidence = 1% per year
• Therefore 150,600 problem drug users
Mortality Multiplier
• Average 40 drug-related deaths in Lithuania– Source: Lithuanian Focal Point Report to the
EMCDDA
• Mortality rate = 1.7%– Source: Most up-to-date study of drug-related
mortality in European Union (data for Denmark)
• 2,350 injecting drug users in Lithuania• 2,940 problem drug users in Lithuania
Capture-recapture method
• Simple idea:– Only a certain proportion of drug users are in contact
with treatment agencies
• Examine the overlap between those in treatment and a second sample (e.g. Police)
• Find the proportion in treatment• Thus estimate the total number of drug users
Capture-recapture Methods
• With two sources we need to assume that the sources are not related to each other
• With three sources we can include relationships between data sources
• Different statistical models are fitted to the data
• We select the ‘best’ model and estimate
Data sources (Vilnius)
• Three distinct sources from the Vilnius Centre for Addictive Disorders– Detoxification with Subutex (n = 207)– Outpatient Treatment (n = 306)– Police sample (n = 166)
• 6 month period within 2006• Opiate users (mostly injectors)• Does not include methadone
substitution
Three-source overlap (Vilnius)
Police Present Absent Outpatient Treatment Present Absent Present Absent Detox Present 4 7 52 144 Absent 24 131 226 -
In total there were 588 ‘visible’ individuals457 were in Detox or Outpatient Treatment
Results (Vilnius)
• 2,167 problem drug users– 95% Confidence Interval = 1,663 – 2,934– Assumes that detox and outpatient sources
are related (but Police data independent)– ‘best’ model and estimate
truncated Poisson method
• Uses a single data source– Number of visits at a syringe exchange
• Number attended once• Number attended twice• Total number who had attended
– Estimates number who have attended zero times
• Assumptions– Attendances are not related to each other– You can identify people who attend more
than once
truncated Poisson analysis (Vilnius)Data for 2006 complete year• Vilnius Centre for Addictive Disorders
– Computerised data– 1,444 people who had used the syringe
exchange provision at any time during 2006
• Estimated 1,622 drug injectors in 2006
truncated Poisson analysis (Vilnius)Data for individual months• Between 250 and 550 individuals
attended in any one month period– More in summer
• Average number of ‘active’ drug injectors each month = 600
truncated Poisson analysis (Klaipeda)• Data from hand written log book (registers)
– Good data– My understanding of Lithuanian alphabet is bad!
• Could only do a monthly analysis• Between 100 and 185 individual attended in
any one month period• Average number of ‘active’ drug injectors
each month = 280• Total number of injectors in Klaipeda = 750
truncated Poisson analysis(Summary)• Vilnius
– 600 ‘active’ injectors per month– 1,663 injectors in 2006
• Klaipeda– 280 ‘active’ injectors per month– 750 injectors in 2006
• Both estimates should be treated with caution– Useful for comparing Vilnius and Klaipeda– Does not contradict capture-recapture analysis
National Estimates
• Use published statistics to extrapolate– Ministry of Interior
• Drug offences
– Lithuanian Focal Point to the EMCDDA • Number of new demands for treatment
– Vilnius Municipality has 50% of national total in both datasets
• Half of Lithuania’s problem drug users live in Vilnius Municipality
National Estimates
• 4,300 problem drug users in Lithuania– 2006 estimate– Problem opiate use
• 3,200 drug injectors– truncated Poisson analysis– 75% injecting
Summary
• These are provisional estimates• The capture-recapture analysis for
Vilnius is as good (if not better) than studies elsewhere in Europe
• The truncated Poisson estimates (for Vilnius and Klaipeda) should be used with caution– But should be reliable for comparing
prevalence rates between the two cities
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