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Methods for providing the first prevalence estimates of opiate use in Western Australia
Abstract
International bodies including the United Nations, the World Health Organisation and the European Monitoring Centre for Drugs and Drug Addiction have highlighted the increasing problem of opiate use and have recommended the truncated Poisson methods and capture-recapture methods, with more than two data sources, for prevalence estimation. This recommendation is difficult to implement however in regions where data sources are limited. The truncated Poisson method, which requires a single data source, is less publicised but is also endorsed by the EMCDDA. Within this paper, we implement both of these methods in Western Australia for the first time. We provide the first multi-source enumeration of opiate prevalence for this region, and in addition develop the two methods for use with in-patient hospital data and police records. We found from the multi-source enumeration that a total of 2826 unique individuals were identified as opiate users in the 2-year study period. In addition, using unstratified capture-recapture models we estimated that the population of hidden opiate users was 17,233 (95% CI of 8960-35,055) during the same period. This gives us a total 2-year prevalence estimate of 20,059 opiate users in Western Australia in the period from the 1st July 1996 to 30th June 1998. This corresponds to an estimated prevalence rate of approximately 18 per 1000 of the population aged between 14 and 55. The need for these methods in the coming decade will increase as we see expansion of the European Union and the increased reporting of drug use in developing and emerging nations.
... The technique has been used in several studies to study the prevalence of problematic drug use, HIV, homelessness and similar problems, particularly since the statistical analyses have been improved and refined (Bloor, 2005;EMCDDA, 1999a;1999b;Hickman et al., 2002;. A number of empirical studies that have specifically examined the prevalence of different kinds of problematic drug use at local and national levels have been conducted over the past dec-ades (Choi & Comiskey, 2003;Domingo-Salvany et al., 1998;Frischer et al., 2001;Gemmell, Millar, & Hay, 2004;Hay, 1997;Hay & Gannon, 2006;Hickman et al., 1999;Hickman et al., 2006;Hser, 1993;Kimber, Hickman, Degenhardt, Coulson, & van Beek, 2008;Maxwell & Pullum, 2001;Millar, Gemmell, Hay, & Donmall, 2004;Kraus et al., 2003;Olsson et al., 1981;Olsson et al., 1994;Olsson et al., 2001;Uhl & Siedler, 2001;Vaissade & Legleye, 2008). ...
... Truncated Poisson can be used to statis-tically calculate and estimate the prevalence of problematic drug use with information from a single source, such as existing information from a health care or correctional treatment register. The method is built on an estimate based on repeated events or care occasions during a certain period (Brå, 2003;Choi & Comiskey, 2003;EMCDDA, 1999a;FHI, 2010;Hay, 2003;Hay & Smit, 2003;Hser, 1993;Kimber et al., 2008). The idea is that the distribution among the individuals occurring once or twice in the register is then applied statistically to calculate those who do not occur at all, which means that nonevents, or those that have hypothetically not yet been observed, can in this way be calculated (i.e. ...
... These studies have had great significance for the assessment of the prevalence of problematic drug use at a national level (for example, Brå, 2003;FHI, 2010). International studies (such as Choi & Comiskey, 2003;Hay, 2003;Hay & Smit, 2003;Hser, 1993;Kimber et al., 2008;Uhl & Seidler, 2001) use the original basic statistical formulas created by Chao and by Zelterman (see Zelterman, 1988;Uhl & Seidler, 2001). ...
Aim
This article analyses and discusses the estimation of serious or problematic drug use through an empirical example based on a local Swedish study in Gothenburg.
Methods and Data
This was a case-finding study with questionnaires directed at organisations which have contact with the target group. The material was supplemented with information from the two documentation systems DOK and ASI. A total of 2,148 reports were collected. Health care data of 1,096 individuals was also collected for analysis with the truncated Poisson method. Analyses with capture-recapture or truncated Poisson were conducted to calculate the size of the hidden population.
Results
The statistical analyses resulted in variable numbers for the hidden population, and the total prevalence of serious drug abuse in Gothenburg is estimated to be between 2,200 and 4,400 people.
Conclusion
The study shows that estimation of the presence and prevalence of problematic drug abuse involves many methodological difficulties and challenges. The significant variation of the size of the hidden population presented in the study raises doubts about the reliability and validity of the different methods. The methods are clearly sensitive to the importance of fulfilling the different basic assumptions.
... Capture-recapture methods have originally been developed in biology to estimate the size of animal populations (Seber 1973;Schwarz and Seber 1999), but have increasingly been integrated into the study of human populations mainly through epidemiological research. Capture-recapture models have been used extensively in the field of substance abuse to estimate the prevalence of drug users susceptible to treatment in a variety of communities (Bohning et al. 2004;Calkins and Atkan 2000;Hser 1993;Choi and Comiskey 2003;Hickman et al. 1999;Smit et al. 1997;Brecht and Wickens 1993). Following the pioneering analyses of Willmer (1970) and Greene and Stollmack (1981) on general populations of offenders, researchers also used capture-recapture methods to estimate populations of burglars (Riccio and Finkelstein 1985), car thieves (Collins and Wilson 1990), prostitutes (Rossmo and Routledge 1990) and their clients (Roberts and Brewer 2006), illegal gun owners (van der Heijden et al. 2003), and drug dealers (Bouchard and Tremblay 2005). ...
... Estimates are differentiated across three cultivation techniques: (1) outdoor, (2) indoor, and (3) hydroponics. Zelterman's model has been used in a handful of studies in the criminological literature but the model's value and limitations are not well understood (Bouchard and Tremblay 2005;Collins and Wilson 1990;Choi and Comiskey 2003;Smit et al. 1997Smit et al. , 2002Bohning et al. 2004). In the current study, the model is used on marijuana cultivation data for an extended time period (5 years). ...
... The wider confidence intervals calculated for hydroponic growers illustrate the fact that capture-recapture estimates become more Notes: Neyman's X 2 is given by X 2 = P n jÀ1 (n j -û j ) 2 nj volatile when used on distributions that depend on lower proportions of recaptures. On the other hand, Zelterman (1988) designed the estimator to be robust especially with this type of data (Choi and Comiskey 2003). Table 3 presents the estimated populations of growers at risk of being arrested between 1998 and 2002 for the two categories found in arrest data: soil-based growers (indoor and outdoor), and hydroponic growers. ...
Originally developed in biology, capture-recapture methodologies have increasingly been integrated into the study of human
populations to provide estimates of the size of “hidden populations.” This paper explores the validity of one capture-recapture
model—Zelterman’s (1988) truncated Poisson estimator—used to estimate the size of the marijuana cultivation industry in Quebec, Canada. The capture–recapture
analysis draws on arrest data to estimate the number of marijuana growers “at risk of being arrested” for a period of five
years (1998–2002). Estimates are provided for growers involved in two different techniques: (1) soil-based growing, and (2)
hydroponics. In addition, the study develops an original method to estimate the prevalence of cultivation sites “at risk of
detection.” A first set of findings shows that the cultivation industry is substantial; the estimated prevalence of growers
compares to estimates of marijuana dealers in the province. Capture–recapture estimates are also used to compare the risks
of being arrested for different types of offenders. Results indicate that hydroponic growers—those involved in large scale
and sophisticated sites—face lower enforcement-related risks than growers involved in smaller enterprises. The significance
of these findings is discussed in the context of the widespread development, both in Europe and in North America, of a successful
domestic production-driven, rather than importation-driven, marijuana trade.
... Pour des raisons pratiques sans doute (disponibilité des connaissances statistiques nécessaires à ce type d'exercice et contraintes dans l'accès à des données colligées dans le format nécessaire à l'estimation) et certainement pour cause d'incertitude quant à la validité des estimations produites (comment savoir si l'estimation se situe près de la réalité ?), ces méthodes ont reçues peu de publicité en criminologie après ces quelques efforts initiaux. L'exception à la règle demeure le milieu des drogues illicites où on a intégré ce type de méthode dans l'estimation des populations de consommateurs « susceptibles » de s'inscrire à des centres de traitements (Bohning et al., 2004 ;Calkins et Atkan, 2000 ;Choi et Comiskey, 2003 ;Smit et al., 1997 ;Hser, 1993 ;Brecht et Wickens, 1993). Ces méthodes « capture et re-capture », traditionnellement développées en biologie pour estimer des populations animales (Seber, 1973), bénéficient d'un engouement récent dans plusieurs domaines de recherche, faisant en sorte que l'on a maintenant une meilleure idée de leur validité pour le type de problème retrouvé en criminologie. ...
... The analytical framework provided by capture-recapture methodologies is suitable to estimate the prevalence of offender populations. A number of studies have relied on the distribution of episodes of treatment to infer the unknown population of treatment "susceptibles" in a given time and place (Woodward, Bonett, and Brecht, 1985;Hser, 1993;Brecht and Wickens, 1993;EMCDDA, 1997;Hay and McKegany, 1996;Hickman, Cox, Harvey, Howes, Farrell, Frischer, Stimson, Taylor, and Tilling, 1999;Calkins and Aktan, 2000;Choi and Comiskey, 2003). Other studies have analyzed the distribution of re-arrests to infer the hidden population of "arrest susceptibles": Greene and Stollmack (1981) used a capture-recapture approach to estimate the population size of offenders in Washington D.C.; Rossmo and Routledge (1990), to estimate the prevalence of prostitutes in Vancouver, Canada; and Collins and Wilson (1990) to estimate the population of car thieves in Victoria, Australia. ...
... Zelterman's (1988) estimator, in particular, has proven to be robust to heterogeneity issues inherent in the study of human populations. Collins and Wilson (1990) have used it with some success to estimate the population of car thieves in an Australian territory, and still others have used it to estimate the prevalence of drug users in a variety of communities (Hser, 1993;EMCDDA, 1997;Choi and Comiskey 2003;Hickman et al., 1998). Bouchard and Tremblay (2005) recently obtained valid population estimates of drug dealers at risk of being arrested in the province of Quebec. ...
"Thèse présentée à la faculté des études supérieures en vue de l'obtention du grade de Ph.D. en Criminologie" Thèse (Ph. D.)--Université de Montréal, 2006.
... First, it starts by estimating the size of the populations involved-here, the prevalence of cannabis growers active in a given year. Even the specific estimation method used in this article (a capture-recapture model) has been widely used to estimate the prevalence of hard drug users (Bohning, Suppawattanabodee, Kusolvisitkul, & Viwaywongkasem, 2004;Calkins & Atkan, 2000;Hser, 1993;Choi & Comiskey, 2003;Hickman, Cox, Havey, Howes, Farrell, Frischer et al., 1998;Smit, Toet, & Van der Heijden, 1997;Brecht & Wickens, 1993). Second, information on cultivation patterns is used to break down the population into categories, depending on growers' productivity rates and the cultivation technique that they use. ...
... Such assumptions when using data on criminal populations may be violated. However, Zelterman's estimator has been shown to be robust with regard to deviations from assumptions, and successful in estimating hidden populations of drugs users (Choi & Comiskey, 2003;Smit et al., 1997;Bohning et al., 2004), drug dealers (Bouchard & Tremblay, 2005), and cannabis growers (Bouchard, 2007). It is given by: ...
Among the many difficulties with estimating the size of the cannabis industry is that suitable methodologies for estimating large-scale outdoor illegal drug production in developing countries cannot be used to estimate indoor production in industrialized countries. This aricle proposes a new approach that overcomes some of these difficulties. The case study is a mature cannabis cultivation industry, located in the province Quebec, Canada. Starting from capture-recapture estimates of the prevalence of growers, the approach combines police and fieldwork data sources on the dynamics of the cultivation industry to correct for typical errors in the assumed productivity rates of different kinds of cultivation sites. Using three different approaches to productivity (ounces-per-plant, yield-per-lamp, yield-per-watt) it was estimated that Quebec cannabis production was approximately 300 tons in 2002; 11% was seized by the police, 33% was consumed within the province, and 56% was potentially exported to the U.S. and to other Canadian provinces.
... First, it starts by estimating the size of the populations involved-here, the prevalence of cannabis growers active in a given year. Even the specific estimation method used in this article (a capture-recapture model) has been widely used to estimate the prevalence of hard drug users (Bohning, Suppawattanabodee, Kusolvisitkul, & Viwaywongkasem, 2004;Calkins & Atkan, 2000;Hser, 1993;Choi & Comiskey, 2003;Hickman, Cox, Havey, Howes, Farrell, Frischer et al., 1998;Smit, Toet, & Van der Heijden, 1997;Brecht & Wickens, 1993). Second, information on cultivation patterns is used to break down the population into categories, depending on growers' productivity rates and the cultivation technique that they use. ...
... Such assumptions when using data on criminal populations may be violated. However, Zelterman's estimator has been shown to be robust with regard to deviations from assumptions, and successful in estimating hidden populations of drugs users (Choi & Comiskey, 2003;Smit et al., 1997;Bohning et al., 2004), drug dealers (Bouchard & Tremblay, 2005), and cannabis growers (Bouchard, 2007). It is given by: ...
Among the many difficulties with estimating the size of the cannabis industry is that suitable methodologies for estimating large-scale outdoor illegal drug production in developing countries cannot be used to estimate indoor production in industrialized countries. This aricle proposes a new approach that overcomes some of these difficulties. The case study is a mature cannabis cultivation industry, located in the province Quebec, Canada. Starting from capture-recapture estimates of the prevalence of growers, the approach combines police and fieldwork data sources on the dynamics of the cultivation industry to correct for typical errors in the assumed productivity rates of different kinds of cultivation sites. Using three different approaches to productivity (ounces-per-plant, yield-per-lamp, yield-per-watt) it was estimated that Quebec cannabis production was approximately 300 tons in 2002; 11% was seized by the police, 33% was consumed within the province, and 56% was potentially exported to the U.S. and to other Canadian provinces.
... First, it starts by estimating the size of the populations involved-here, the prevalence of cannabis growers active in a given year. Even the specific estimation method used in this article (a capture-recapture model) has been widely used to estimate the prevalence of hard drug users (Bohning, Suppawattanabodee, Kusolvisitkul, & Viwaywongkasem, 2004;Calkins & Atkan, 2000;Hser, 1993;Choi & Comiskey, 2003;Hickman, Cox, Havey, Howes, Farrell, Frischer et al., 1998;Smit, Toet, & Van der Heijden, 1997;Brecht & Wickens, 1993). Second, information on cultivation patterns is used to break down the population into categories, depending on growers' productivity rates and the cultivation technique that they use. ...
... Such assumptions when using data on criminal populations may be violated. However, Zelterman's estimator has been shown to be robust with regard to deviations from assumptions, and successful in estimating hidden populations of drugs users (Choi & Comiskey, 2003;Smit et al., 1997;Bohning et al., 2004), drug dealers (Bouchard & Tremblay, 2005), and cannabis growers (Bouchard, 2007). It is given by: ...
... The effectiveness of policy interventions often hinges on knowing the size of the target population. The most extensive body of research in this area considers the number of problem drug users (e.g., Bouchard & Tremblay, 2005;Brecht & Wickens, 1993;Choi & Comiskey, 2003), which informs the size of facilities, staffing, and funding needed to subsidize treatment programs. ...
The size of criminal populations is unknown, and policy decisions are typically based only on the number of offenses and offenders that come to the attention of the criminal justice system. However, the size of criminal populations may follow different trends than what is observed in official data. We use a regression-adjusted capture–recapture model to estimate the number of people at risk of arrest for offenses involving amphetamine-type stimulants (ATS) from arrests and rearrests occurring in Quebec, Canada, controlling for year of first arrest, age, and gender. The 4,989 individuals arrested were the visible part of an estimated 42,541 [36,936, 48,145] individuals otherwise at risk of arrest (12%). Additional results show that trends in criminal populations and risks of arrest vary across offense type and drug classifications.
... Prevalence rates of opiate use disorders among adults in different parts of the world have been estimated to be less than 1% (Choi & Comiskey, 2003;Kraus et al., 2003). Once the disorder develops, it usually persists for several years and the typical pattern is brief periods of abstinences followed by relapse. ...
The purpose of this study is to assess the relative mediating effects of impulsivity and emotion dysregulation in the relationship between childhood maltreatment and motives for opiate use. Seventy four adolescent users of Tramadol, a synthetic opiate, were recruited from a boot camp for de-addiction and rehabilitation services for the study. Data were collected between May, 2014 and November, 2014. Participants completed assessments of childhood abuse history, difficulties regulating emotions, impulsiveness and motives for substance use as well as a socio-demographic information sheet. The results of the current study indicate that types of abuse may be associated with particular outcomes and can inform treatment planning for substance users. Findings from bootstrap mediator analyses indicated that emotion dysregulation, but not impulsiveness, mediated the relationship between childhood emotional abuse and expansion and enhancement motives for substance use. The current study provides preliminary evidence that difficulties regulating emotions may function as a mechanism linking prior childhood experiences of emotional abuse to subsequent motives for substance use. Clinical implications of these findings suggest that targeting emotion dysregulation problems may be an effective adjunct in the treatment of childhood emotional abuse adolescent victims at risk for substance use. Published by Elsevier Inc.
... One of these methods is the truncated count models which have a lot of advantages such as more precise estimation, simplicity, and making use of available data [8] . Such advantages caused this method to be used extensively in areas of public health and epidemiologic studies like estimation of the numbers of criminals [9,10] , of drug abusers [11][12][13][14] , and of homosexuals [15] . ...
Objectives:
Rates of Deliberate Self-Poisoning (DSP) attempts are subjected to under-counting, under-reporting, and denying suicide attempts. In this study, therefore, we seek to estimate the rate of under-reported DSPs, which is the most common way of suicide attempts in Iran.
Methods:
Using truncated count models, we estimated rates and numbers of under-counted DSP attempts in western part of Iran in 2015. By this method, n0, namely the number of people attempted DSP, but not referring to any health care centers, was calculated through data connection. Then, crude and adjusted age rates of DSP attempts were estimated directly using average population of respective city and standard world population with and without taking under-reporting into account. Monte Carlo method was used to determine confidence level.
Results:
Completeness of data recorded to estimate the number of people attempting DSP was obtained in the range of 46.6%_53.2% by using different methods Rates of under-reported cases were higher among women than men and decreased as age increased. Rates of under-reported decreased with an increase in potency and intensity of toxic factors. Maximum under-reported rates of 69.9%, 51.2% and 21.5% were observed with oil and detergents (x66), medications (x60_64) and agricultural toxins (x68, 69), respectively. Crude rates, with and without considering under-reporting, were obtained by mixture method at 167.5 and 331.7 per 100,000 in order, which decreased to 129.8 and 251.3 per 100,000, respectively, after adjusting age on the basis of standard population given by WHO.
Conclusion:
Nearly half of individuals attempted DSP did not referred to the hospital for treatment or denies SA for political and social-cultural reasons. Individuals without any consultation services are at higher risks of repeated suicide attempts and fatal suicides.
... [47][48][49] En particulier, dans l'évaluation des populations « hors-la-loi » où les hypothèses de la distribution de Poisson peuvent ne pas être respectées. [49][50][51] La méthode de capture-recapture utilisant une source est simple, mais requiert une base de données identifiant correctement la distribution des données de capture. Car la logique de cette méthode de capture-recapture se fonde sur l'idée que le taux de capture prévu pour les UDI qui ne sont pas encore connus est plus près du taux établi pour les UDI ayant eu une ou deux visites. ...
... For this reason, four-source analyses were carried out, treating each year's data from treatment and police as a separate source. Other studies have also increased the effective number of sources by using the same source in different periods of time [17][18][19]. For each stratified analysis, the simplest 22 models were fitted; these models had up to two two-way interactions between data sources. ...
Introduction and aims:
Information on high-risk drug use in Turkey, particularly at the regional level, is lacking. The present analysis aims at estimating high-risk cannabis use (HRCU) and high-risk opiate use (HROU) in the cities of Ankara, Istanbul and Izmir.
Design and methods:
Capture-recapture and multiplier methods were applied based on treatment and police data stratified by age and gender in the years 2009 and 2010. Case definitions refer to ICD-10 cannabis (F.12) and opiate (F.11) disorder diagnoses from outpatient and inpatient treatment records and illegal possession of these drugs as recorded by the police.
Results:
High-risk cannabis use was estimated at 28 500 (8.5 per 1000; 95% confidence interval 7.3-10.3) and 33 400 (11.9 per 1000; 95% confidence interval 10.7-13.5) in Ankara and Izmir, respectively. Using multipliers based on capture-recapture estimates for Izmir, HRCU in Istanbul was estimated up to 166 000 (18.0 per 1000; range: 2.8-18.0). Capture-recapture estimates of HROU resulted in 4800 (1.4 per 1000; 95% confidence interval 0.9-1.9) in Ankara and multipliers based on these gave estimates up to 20 000 (2.2 per 1000; range: 0.9-2.2) in Istanbul. HROU in Izmir was not estimated due to the low absolute numbers of opiate users.
Discussion and conclusions:
While HRCU prevalence in both Ankara and Izmir was considerably lower in comparison to an estimate for Berlin, the rate for Istanbul was only slightly lower. Compared with the majority of European cities, HROU in these three Turkish cities may be considered rather low. [Kraus L, Hay G, Richardson C, Yargic I, Ilhan N M, Ay P, Karasahin F, Pinarci M, Tuncoglu T, Piontek D, Schulte B Estimating high-risk cannabis and opiate use in Ankara, Istanbul and Izmir Drug Alcohol Rev 2016;00:000-000].
... For example, the same source of information in each trimester of the year was counted as four mark-recapture sources in Domingo-Salvany et al. (1995). The same device has also been used over two-year study periods in order to obtain first estimates in places where data sources are limited (Choi andComiskey, 2011, Kraus et al., 2011). ...
Sparked by the need to inform the response to the spread of HIV/AIDS in drug-injecting populations in the 1980s and the desire to base local, national and international responses to tackling drug use in the 1990s on solid epidemiological data, the mark-recapture method has increasingly been used to estimate the prevalence of drug use. Richard Cormack provided support and advice to some of the first United Kingdom and European studies to estimate drug use prevalence in this way. The approach he outlined, using macros that he developed, has led to the mark-recapture method being used to systematically assess the use of drugs such as heroin or other opioids in the United Kingdom and across Europe. We review the development of the method when applied to estimating the size of drug-using populations, including the use of Bayesian methods. We discuss its limitations and various criticisms that have been voiced.
... Prevalence rates of opiate use disorders among adults in different parts of the world have been estimated to be less than 1% (Choi & Comiskey, 2003;Kraus et al., 2003). Once the disorder develops, it usually persists for several years and the typical pattern is brief periods of abstinences followed by relapse. ...
The purpose of this study is to assess the relative mediating effects of impulsivity and emotion dysregulation in the relationship between childhood maltreatment and motives for opiate use. Seventy four adolescent users of Tramadol, a synthetic opiate, were recruited from a boot camp for de-addiction and rehabilitation services for the study. Data were collected between May, 2014 to November, 2014. Participants completed assessments of childhood abuse history, difficulties regulating emotions, impulsiveness and motives for substance use as well as a socio-demographic information sheet. The results of the current study indicate that types of abuse may be associated with particular outcomes and can inform treatment planning for substance users. Findings from bootstrap mediator analyses indicated that emotion dysregulation, but not impulsiveness, mediated the relationship between childhood emotional abuse and expansion and enhancement motives for substance use. The current study provides preliminary evidence that difficulties regulating emotions may function as a mechanism linking prior childhood experiences of emotional abuse to subsequent motives for substance use. Clinical implications of these findings suggest that targeting emotion dysregulation problems may be an effective adjunct in the treatment of childhood emotional abuse adolescent victims at risk for substance use.
... [47][48][49] En particulier, dans l'évaluation des populations « hors-la-loi » où les hypothèses de la distribution de Poisson peuvent ne pas être respectées. [49][50][51] La méthode de capture-recapture utilisant une source est simple, mais requiert une base de données identifiant correctement la distribution des données de capture. Car la logique de cette méthode de capture-recapture se fonde sur l'idée que le taux de capture prévu pour les UDI qui ne sont pas encore connus est plus près du taux établi pour les UDI ayant eu une ou deux visites. ...
Background: To plan and implement services to persons who inject drugs (PWID), knowing their number is essential. For the island of Montréal, Canada, the only estimate, of 11,700 PWID, was obtained in 1996 through a capture-recapture method. Thirteen years later, this study was undertaken to produce a new estimate. Methods: PWID were defined as individuals aged 14-65 years, having injected recently and living on the island of Montréal. The study period was 07/01/2009 to 06/30/2010. An estimate was produced using a six-source capture-recapture log-linear regression method. The data sources were two epidemiological studies and four drug dependence treatment centres. Model selection was conducted in two steps, the first focusing on interactions between sources and the second, on age group and gender as covariates and as modulators of interactions.
Results: A total of 1,480 PWID were identified in the six capture sources. They corresponded to 1,132 different individuals. Based on the best-fitting model, which included age group and sex as covariates and six two-source interactions (some modulated by age), the estimated population was 3,910 PWID (95% confidence intervals (CI): 3 180-4 900) which represents a prevalence of 2.8 (95% CI: 2.3-3.5) PWID per
1000 persons aged 14-65 years. Conclusions: The 2009-2010 estimate represents a two thirds reduction compared to the one for 1996. The multisource capture-recapture method is useful to produce estimates of the size of the PWID population. It is of particular interest when conducted at regular intervals thus allowing for close monitoring of the injection phenomenon.
... In the field of illicit drug research, the one-list approach has been applied to estimate prevalence of specific subpopulations of drug users such as: opiate users in Rotterdam [28], opiate users in Western Australia [29], heroin and metamphetamine users in Bangkok [30], problematic cocaine users in Barcelona [31], problem drug users [32], prevalence of cocaine users in Italy [33]. ...
A comparative analysis of three different estimation methods of cocaine use in Milan, Italy, is carried out, including an analysis of the size and trends of the underlying reference population. The three cocaine use estimates are derived from wastewater analysis, a "street" survey and one-source capture-recapture analysis of administrative sanctions for drug possession. All three data sources span several years during the decade 2000-2010. For each method, assumptions and limitations are discussed. It is concluded, although the amount of data regarding cocaine use in Milan during the years 2000-2010 is considerable, that none of the estimates is completely reliable, mainly because of the many assumptions needed for inference to the whole community, that all three estimates however agree on a substantial reduction in cocaine use and users between the years 2007 and 2010. The recently developed wastewater analysis technique yields estimates comparable to those derived from the street based survey, while capture-recapture analysis of administrative data on identification by law enforcement agencies as cocaine user probably targets only a subpopulation of all users.
... The first, introduced in Section 1, is about heroin users in Bangkok metropolitan region, labeled as HUBM. The second, provided by the police service, is about heroin users in Western Australia from July 1st, 1997 to June 30th, 1998, labeled as HUWA (Choi and Comiskey, 2003). ...
Estimating population sizes via capture-recapture experiments has enormous applications. The Poisson mixture model can be adopted for those applications with a single list in which individuals appear one or more times. We compare several nonparametric estimators, including the Chao estimator, the Zelterman estimator, two jackknife estimators and the bootstrap estimator. The target parameter of the Chao estimator is a lower bound of the population size. Those of the other four estimators are not lower bounds, and they may produce lower confidence limits for the population size with poor coverage probabilities. A simulation study is reported and two examples are investigated.
... Indirect estimation techniques tend to build upon existing data and their mutual relationship in order to estimate the number of non-observed cases in a given population. The latter include capture-recapture techniques [1][2][3][4][5][6][7][8] , benchmark-multiplier methods [1,[9][10][11] , the truncated Poisson method [1,12,13] , and the multivariate indicator method [14][15][16][17][18][19] . However, none of currently known methods is considered to be the gold PDU/IDU Prevalence in Luxembourg Eur Addict Res 2012;18:288-296 289 standard since they all rely on a series of assumptions and limitations [20] . ...
Background:
To estimate the prevalence of problem drug use (PDU) and injecting drug use (IDU) in Luxembourg and analyze trends between 1997 and 2009. To assess the feasibility of prevalence estimations based on drug use surveillance systems.
Methods:
Serial multi-method PDU/IDU prevalence estimations based upon capture-recapture, Poisson regression, multiplier and back-calculation methods. Comparative analysis of methods and assessment of their robustness to variations of external factors.
Results:
National PDU and IDU prevalence rates were estimated at 6.16/1,000 (95% CI 4.62/1,000 to 7.81/1,000) and 5.68/1,000 (95% CI 4.53/1,000 to 6.85/1,000) inhabitants aged 15-64 years, respectively. Absolute prevalence and prevalence rates of PDU increased between 1997 and 2000 and declined from 2003 onwards, whereas IDU absolute prevalence and prevalence rates witnessed an increasing trend between 1997 and 2007.
Conclusions:
Drug use surveillance systems can be valuable instruments for the estimation and trend analysis of drug misuse prevalence given multiple methods are applied that rely on serial and representative data from different sources and different settings, control multiple counts and build upon standardized and sustained data collection routines. The described institutional contact indicator revealed to be a useful tool in the context of PDU/IDU prevalence estimations and thus contributes to enhancing evidence-based drug policy planning.
... There are also simpler closed models (e.g. truncated Poisson) [17][18][19]. The closure assumption (i.e. ...
(i) To compare indirect estimation methods to obtain mean injecting drug use (IDU) prevalence for a confined geographic location; and (ii) to use these estimates to calculate IDU and injection coverage of a medically supervised injecting facility.
Multiple indirect prevalence estimation methods.
Kings Cross, Sydney, Australia.
IDUs residing in Kings Cross area postcodes recorded in surveillance data of the Sydney Medically Supervised Injecting Centre (MSIC) between November 2001 and October 2002.
Two closed and one open capture-recapture (CRC) models (Poisson regression, truncated Poisson and Jolly-Seber, respectively) were fitted to the observed data. Multiplier estimates were derived from opioid overdose mortality data and a cross-sectional survey of needle and syringe programme attendees. MSIC client injection frequency and the number of needles and syringes distributed in the study area were used to estimate injection prevalence and injection coverage.
From three convergent estimates, the mean estimated size of the IDU population aged 15-54 years was 1103 (range 877-1288), yielding a population prevalence of 3.6% (2.9-4.3%). Mean IDU coverage was 70.7% (range 59.1-86.7%) and the mean adjusted injection coverage was 8.8% (range 7.3-10.8%). Approximately 11.3% of the total IDU population were estimated to be new entrants to the population per month.
Credible local area IDU prevalence estimates using MSIC surveillance data were obtained. MSIC appears to achieve high coverage of the local IDU population, although only an estimated one in 10 injections occurs at MSIC. Future prevalence estimation efforts should incorporate open models to capture the dynamic nature of IDU populations.
Prevalence indicators are a fundamental tool to measure the size and the dynamics of drug markets. Capture-recapture methods are increasingly being applied to estimate these indicators for human populations that are difficult to count by conventional means. In the present intervention, we compare different capture-recapture procedures aiming to estimate the size of drug users population, at risk of cautioning, in Italy in the year 2007. Data sets are provided by the Italian Ministry of Interiors. In order to evaluate the impact of policies, particular attention is devoted to prevalence estimates for lower age classes (under 20 years), where prevalence can be considered as a good proxy of incidence.
A generic globally applicable integral equation allows the estimation of hidden drug use. Formulas for estimating the prevalence of drug use are provided for both the assumed and known latency period. Estimates of prevalence of opiate use in Ireland ranging from 7,955 [5,789, 10,122] to 11,986 [8,792, 15,181] with prevalence rates ranging from 2.7 [2.0, 3.5] per 1,000 to 4.1 [3.0, 5.2] were obtained. The model can be implemented by service providers and planners if numbers of first treatments for drug use and the latency period are known or assumed.
This paper reviews major challenges in the conceptual clarification and empirical inquiry of labor trafficking. Much of current literature on human trafficking in the U.S. has focused on the sexual exploitation of women and children. As a result, government funding has mostly gone to law enforcement agencies and rescue agencies home and abroad to find these victims. International organizations believe labor trafficking is perhaps far more prevalent than sex trafficking. But empirical research on labor trafficking remains rare. Wild claims have instead taken place of rigorous empirical research in advocacy activities and policy making. This paper calls for greater efforts on primary data collection that measures the incidence and prevalence of labor trafficking activities in the U.S. Campaigns against human trafficking cannot be sustained or even remain credible without sound empirical research.
This research shows that current information about cyber-fraud is being funneled to a variety of different organizations, including banks, regulatory agencies and various police agencies, or is simply not recorded. There is a clear shortage of data measuring the prevalence and costs of cyber-fraud in Canada and the available information is incomplete and fragmented. The lack of reporting of cyber-fraud incidents by individual and corporate/government victims means that many cases are not recorded or represented in official crime statistics. This research demonstrates a strong need for the creation of a national centre to record and measure data relating to cyber-fraud across Canada. A central databank of known cyber-fraud offenders and cases across the country could facilitate the identification and tracking of suspects in cyber-fraud cases and could further understanding regarding when one individual, or group of individuals, is committing fraud all over the country. Ultimately, a national databank on cyber-fraud incidents could give law enforcement officials a better understanding of the types of cyber-fraud being committed in Canada.
In a climate of signifi�cant problem drug use opiates, notably heroin continue to be the main problem drugs. Illegal drug use is clearly a hidden phenomenon which makes it very diff�cult to obtain accurate estimates of untreated use. Yet viable cost �effective methods to produce current and regular geographically distributed prevalence and incidence estimates are required by policy makers and service providers responsible for allocating increasingly scarce resources in a worldwide recession.
Using Irish data on over 6,000 cases of clients presenting for �first treatment Gamma and Weibull incubation period distributions describing progression to �first treatment were �fitted. This was then applied with new analytical solutions of the back calculation equation and a linear Volterra integral equation to project back and estimate for the fi�rst time the untreated population of opiate users. An integral equation model was derived to estimate the prevalence of opiate use based on the models derived for the hidden incidence of opiate use. These were solved and estimates of the prevalence of opiate use were produced for situations where the exact rate of progression to treatment were unknown and known. Using the prevalence estimates produced and partial di�fferential equations a model was derived to describe the geographic spread of opiate use in Ireland.
The methods and solutions produced address the very real problem facing health service providers and planners in tackling and providing adequate services for the ongoing problem of opiate use in Ireland.
Drawing upon innovative research methods this article provides the first Irish estimates of opiate use based entirely on non-medical data. These estimates are based on the report Baseline Findings from the ROSIE Study by Comiskey and Cox (2005), commissioned in 2002 by the Irish Government's National Advisory Committee on Drugs (NACD). In order to place these estimates in context we first provide a background to the probation and welfare service in Ireland; we then provide a picture of known opiate use to date; and finally we introduce the methods we used to provide new results on the prevalence of opiate users in Ireland.
Estimates of the prevalence of problem drug use, defined within this study as the illicit use of opiates or benzodiazepines, have been provided for all 32 local government areas in Scotland. A national prevalence estimate has been derived as the sum of the local estimates.Data on individual drug users were collated from the police, social work departments, general practitioners, drug treatment services. These data were augmented by the Scottish Drug Misuse Database. In total 22,795 individuals were identified as opiate or benzodiazepine users. This figure corresponds to 0.8% of the population aged 15 to 54.In terms of the national prevalence of problem drug use, it was estimated that there were 55,800 individuals illicitly using opiates and benzodiazepines in Scotland in the year 2000 (95% CI: 43,591–77,697%). That figure corresponds to 2.0% (95% CI: 1.5–2.7%) of the population aged 15 to 54. The local prevalence rates, derived from capture–recapture estimates, ranged from 0.8 to 3.8%.This study has demonstrated that it is possible to use the capture–recapture method in urban and rural areas and, by systematically applying this method at the local level, a national prevalence estimate can be obtained.
Capture-recapture methodologies have been used to estimate the size of the hidden population of active offenders on the basis of the observed properties of the truncated distribution of arrested offenders. We use this approach to estimate the odds of arrest of marijuana, cocaine, crack, and heroin dealers and users in one Canadian province (Quebec). Findings indicate that risks of being arrested are much higher for sellers than for consumers and that this gap widens for the more harmful drugs. Findings also show, however, that vulnerability to arrest was significantly higher for marijuana users than for others users and that dealers in the smaller but more harmful drug markets (crack and heroin) manage to experience lower aggregate risks of arrest than cocaine or marijuana dealers.
Aims: The aim of this study was to establish prevalence estimates of problem drug use, defined as opiate and/or crack cocaine use by persons aged 15 to 64 years, for England and for each of the 149 administrative areas responsible for commissioning drug interventions. Methods: Indirect estimation techniques, the capture–recapture and multiple indicator methods, were used to obtain estimates. Information on problem drug users presenting to healthcare settings and/or recorded by the criminal justice system, and drug-related indicator data were used in the analyses. Findings: There were an estimated 332,090 problem drug users in England during 2005/06 (95% CI 324,546 to 346,345), equivalent to 9.97 (95% CI 9.74 to 10.40) problem drug users per thousand population aged 15 to 64 years. Prevalence varied by geographic region and age group: the highest rates were observed in London and for those aged 25 to 34 years. Conclusions: This study has produced estimates of the prevalence of problem drug use in England that are more robust, more precise, and suggest a higher prevalence than previous studies. The estimates provide a basis on which to formulate policy, plan services, and measure service performance.
This study sought to estimate the prevalence of injecting drug users (IDU) in Togliatti city and to examine the implications of these estimates for HIV prevalence and harm reduction.
Routine data sources of IDUs were identified. Covariate capture-recapture techniques were used on the individuals identified on the three data sources and used to estimate the number of IDU 'not observed' by the data sources, and thereby estimate the prevalence of IDU.
Togliatti City, Samara Oblast, Russian Federation.
IDUs recorded on three data sources (narcology records, HIV positive test results and police arrest data) during 2001.
Poisson regression models were fitted to the observed data, with interactions between data sources fitted to replicate 'dependencies' between those data sources. To select the best model the goodness of fit was approximated by chi2 distribution and the best-fitting model was selected on the basis of standard information criteria and log likelihood ratio tests.
The total estimated population of IDUs is 20 226 [95% confidence interval (CI): 16 971-24 749] giving a population prevalence of 5.4% (95% CI: 4.5-6.6%) of the registered population and 2.7% (95% CI: 2.4-3.5%) of the population (including migrants) aged 15-44 years. For every one IDU in contact with a service there were three out of contact.
There is a high prevalence of IDU which, in the context of a fast-emerging IDU-associated HIV epidemic, will have serious public health implications.
This paper provides the first estimates of recorded and hidden prevalence of opiate use among young people in Dublin. It explores the nature of other drugs used and their effect on the decision to leave school early. The author implements the first multisource enumeration of opiate use in young people in Dublin in 1996 and 1997. Hidden prevalence is estimated by the capture-recapture methodology. The nature of other drugs used was examined by surveying early school leavers. A minimum of 1528 young people aged between 10 and 20 years were identified as using opiates through three 1996 data sources. Using three samples it was estimated that 4081 (95% CI of 3586-4692) were using opiates in Dublin in 1996. Using two samples it was estimated that 1141 (95% confidence interval (CI) of 901-1381) of these were problematic users. Using the two-sample method it was estimated that this rose to 1315 problematic users in 1997. It was found that 51.1% of those surveyed had tried using drugs before they had left school and 46.5% noted that this use had affected them while they attended school. The implications for policy of the size of the opiate problem among young people of school age is considerable.
A point estimator and its associated confidence interval for the size of a closed population are proposed under models that incorporate heterogeneity of capture probability. Real data sets provided in Edwards and Eberhardt (1967, Journal of Wildlife Management 31, 87-96) and Carothers (1973, Journal of Animal Ecology 42, 125-146) are used to illustrate this method and to compare it with other estimates. The performance of the proposed procedure is also investigated by means of Monte Carlo experiments. The method is especially useful when most of the captured individuals are caught once or twice in the sample, for which case the jackknife estimator usually does not work well. Numerical results also show that the proposed confidence interval performs satisfactorily in maintaining the nominal levels.
To apply capture-recapture methods to provide an estimate of the prevalence of opiate and benzodiazepine misuse in Dundee, Scotland.
A four sample capture-recapture method using data from both statutory and non-statutory data sources to estimate drug misuse prevalence in Dundee between January 1990 and December 1994.
Users of benzodiazepines or opiates residing within Dundee.
Altogether 855 drug misusers were identified from various sources within Dundee; many were identified from more than one source. Using this data, the estimated unknown population was 1702, giving a total population of 2557 (95% confidence interval (CI) 1974, 3458) who misuse benzodiazepines or opiates. This represents a prevalence of 28.8 (95% CI 22.3, 39.0) per thousand.
Capture-recapture techniques can be applied to statutory and non-statutory agency data to produce an estimate of at least certain sections of the drug misusing population. However, it is important to recognise the limitations of this methodology and in future to seek to combine a range of approaches to the problem of estimating prevalence rather than sticking rigidly to any single approach.
In log-linear capture-recapture approaches to population size, the method of model selection may have a major effect upon the estimate. In addition, the estimate may also be very sensitive if certain cells are null or very sparse, even with the use of multiple sources. The authors evaluated 1) various approaches to the issue of model uncertainty and 2) a small sample correction for three or more sources recently proposed by Hook and Regal. The authors compared the estimates derived using 1) three different information criteria that included Akaike's Information Criterion (AIC) and two alternative formulations of the Bayesian Information Criterion (BIC), one proposed by Draper ("two pi") and one by Schwarz ("not two pi"); 2) two related methods of weighting estimates associated with models; 3) the independent model; and 4) the saturated model, with the known totals in 20 different populations studied by five separate groups of investigators. For each method, we also compared the estimate derived with or without the proposed small sample correction. At least in these data sets, the use of AIC appeared on balance to be preferable. The BIC formulation suggested by Draper appeared slightly preferable to that suggested by Schwarz. Adjustment for model uncertainty appears to improve results slightly. The proposed small sample correction appeared to diminish relative log bias but only when sparse cells were present. Otherwise, its use tended to increase relative log bias. Use of the saturated model (with or without the small sample correction) appears to be optimal if the associated interval is not uselessly large, and if one can plausibly exclude an all-source interaction. All other approaches led to an estimate that was too low by about one standard deviation.
Public health planning continues to be troubled by the uncertainty of the extent of hidden drug use. Methods for estimating the prevalence of opiate use are discussed. These include multisource enumeration, death multiplier, multiple indicator, and capture-recapture methods. The feasibility and data requirements for each of these methods is illustrated for the first time in an Irish context. Estimates presented are the result of years of intensive collaboration between previously unconnected government, health, and legal agencies. Finally, the implications of the methods and their results for the planning and provision of medical and social policy are highlighted and discussed.
To date there have been no studies estimating the hidden prevalence of opiate use in Dublin.
A multisource enumeration followed by the application of the capture-recapture method with log-linear modelling including age and gender stratification to remove heterogeneity was implemented to provide an estimate of the unknown size of the opiate-using population. Two medical and one legal data sources were used.
It was found that the ratio of known to unknown opiate users was 1:1.15 with a total of 13,460 (95% CI: 12,037-15,306) users estimated in Dublin in 1996.
The findings of this study have important ramifications for service delivery.
This paper reviews the historical background and the theoretical development of models for the analysis of data from capture-recapture or multiple-record systems for estimating the size of closed populations. The models and methods were originally developed for use in fisheries and wildlife biology and were later adapted for use in connection with human populations. Application to epidemiology came much later. The simplest capture-recapture model involves two lists or samples and has four key assumptions: that the population is closed, that individuals can be matched from capture to recapture, that capture in the second sample is independent of capture in the first sample, and that the capture probabilities are homogeneous across all individuals in the population. Log-linear models provide a convenient representation for this basic capturerecapture model and its extensions to K lists. The paper provides an overview for these models and illustrates how they allow for dependency among the lists and heterogeneity in the population. The use of log-linear models for estimation in the presence of both dependence and heterogeneity is illustrated on a four-list example involving ascertainment of diabetes using data gathered in 1988 from residents of Casale Monferrato, Italy. The final section of the paper discusses techniques for model selection in the context of models for estimating the size of populations. Am J Epidemiol 1995;142:1047–58.
A new estimate of the size of a closed population when the samples are of size one is considered. It is adapted from Robbins's estimate of the total probability of the unobserved outcomes of an experiment and is interesting because of its high efficiency. The bias and variance of the new estimate, and those of the maximum likelihood estimate, are examined numerically.
One way in which a capture-recapture experiment can be designed is to count each capture occasion as a separate sample, and tally the number of individuals caught once, twice, and so on. This paper discusses the estimators currently used for this type of experiment, and suggests some new ones. Each of the estimators is categorized by its derivation. Following this, their properties are discussed, particularly their bias and variance, with the aim of choosing one or two of the estimators which are the 'best' to use, especially in handling a heterogeneous population. It is found that the bias adjusted estimator of Chao (1989) is the best to use when the number of captures is relatively small, and that the estimator of Darroch & Ratcliff (1980) should be used otherwise.
Describes several important quantitative procedures for estimating the size of an unobserved or partially observed population, with specific application to the estimation of the prevalence of drug use. Methods discussed include synthetic estimation, truncated Poisson estimates, multiple-capture surveys in closed populations (the capture–recapture model and log-linear models) and open populations (the Jolly-Seber model [G. M. Jolly, 1965; G. A. Seber, 1965] and Markov models), and system dynamics models. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Estimators of population size under two commonly used models (the time- variation model and the heterogeneity model) for sparse capture-recapture data are proposed. A real data set of Illinois mud turtle (Kinosternon flavescens spooneri) is used to illustrate the methods and to compare them with other estimators. A simulation study was carried out to show the performance and robustness of the proposed estimators.
A family of estimators is proposed for the relative frequency of the unobservable zero class in a truncated Poisson distribution. Large sample behavior is described by asymptotic expansion and robust properties are discussed in the presence of compound distributions. Two applications are presented involving the estimation of the number of unobserved individuals in complex capture-recapture experiments.
This article evaluates the potential epidemiologic uses of capture-recapture, which include the primary area of determining disease frequency. Capture-recapture may be a means to effectively “count” new cases (incidence) or count existing cases (prevalence). Specific applications of capture-recapture in epidemiology are presented, one of which is its use in estimating death rates in a region close to Calcutta, India. The method also has considerable potential to assess suicides, and it may be the only technique to assess disease frequency in developing countries. In addition to generating an estimate of population size, another application of capture-recapture is to assess the costs of ascertainment relative to the degree of accuracy. This approach provides a formal means for assessing the cost-benefits of lists for the identification of cases. The authors believe that with careful and appropriate use, capture-recapture methods will provide a new approach that can considerably improve our ability to monitor disease. Am J Epidemiol 1995;142:1059–68.
The prevalence of injecting drug use in Glasgow during 1989 was derived using log-linear analysis to model the relationship between unnamed identifier information obtained from Strathclyde Police, the Scottish HIV-test Reporting Scheme and Treatment Agencies. Whereas previous attempts have required, although rarely demonstrated, independence between samples, the method adopted here did not necessitate this assumption. The best model resulted from taking the dependency between the HIV-test and treatment samples into account, and yielded an estimate of 9424 (95% confidence interval +/- 2460), which represents 11-19 per 1000 population aged 15-55 in Glasgow. The estimated male:female ratio was 2.64:1 and the modal injecting drug user (IDU) aged 20-24. While there are no indicators that prevalence has begun to decline, the extent of the hidden population suggests that around 1 in 7 were receiving some form of treatment for drug use. Available evidence suggests that buprenorphine, temazepam and amphetamines, rather than heroin, are the most commonly injected drugs. These findings should facilitate assessment of the service requirements of this group, and provide a basis from which the number of IDUs infected with HIV and the number likely to progress to AIDS can be determined.
It is difficult to obtain accurate prevalence estimates of opiate addiction with direct methods. The capture-recapture method has been used to estimate the prevalence of hidden populations, including opiate addicts. In this study, we applied capture-recapture, including log-linear modeling, to estimate the prevalence of opiate addicts in Barcelona, Spain. Anonymous identification data from three 1989 sources (hospital emergency rooms, treatment admissions, and heroin overdose deaths) in Barcelona were used to obtain population samples. For prevalence estimation, two strategies were followed: 1) emergency room data only, divided into trimesters; and 2) all three sources used simultaneously. Estimates based only on emergency room data were lower than estimates obtained by the simultaneous analysis of all three data sources; the latter estimates gave narrower confidence intervals (6,324-7,414 addicts), giving a prevalence for Barcelona in 1989 of between 8.5 and 9.9 opiate addicts per 1,000 residents aged 15-44 years. The estimated prevalence varied by sex and age group and was highest in males aged 15-29 years (between 17.1 and 21.2). At least 42% had contacted one or more of the services studied, although only one in seven had been admitted for treatment during 1989. Capture-recapture is the election method for prevalence estimation when direct methods are not feasible.
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