Estimating the Size of Hidden Populations Using Respondent-driven Sampling Data: Case Examples from Morocco.

BACKGROUND: Respondent-driven sampling is used worldwide to estimate the population prevalence of characteristics, such as HIV/AIDS and associated risk factors in hard-to-reach populations. Estimating the total size of these populations is of great interest to national and international organizations; however, reliable measures of population size often do not exist. METHODS: Successive sampling-population size estimation (SS-PSE) along with network size imputation allows population size estimates to be made without relying on separate studies or additional data (as in network scale-up, multiplier, and capture-recapture methods), which may be biased. RESULTS: Ten population size estimates were calculated for people who inject drugs, female sex workers, men who have sex with other men, and migrants from sub-Saharan Africa in six different cities in Morocco. SS-PSE estimates fell within or very close to the likely values provided by experts and the estimates from previous studies using other methods. CONCLUSIONS: SS-PSE is an effective method for estimating the size of hard-to-reach populations that leverages important information within respondent-driven sampling studies. The addition of a network size imputation method helps to smooth network sizes allowing for more accurate results. However, caution should be used particularly when there is reason to believe that clustered subgroups may exist within the population of interest or when the sample size is small in relation to the population.

Prevalence and behavioural risks for HIV and HCV infections in a population of drug users of Dakar, Senegal: the ANRS 12243 UDSEN study.

OBJECTIVES: Data on the extent of drug use and associated HIV, hepatitis C and hepatitis B infection in West Africa are lacking. The objectives of ANRS12244 UDSEN study were to estimate the size of the heroin and/or cocaine drug user (DU) population living in the Dakar area (Senegal), and assess the prevalence and risk factors of HIV, hepatitis C virus (HCV) and hepatitis B virus (HBV), including behavioural determinants in this population, in order to set up an integrated prevention and treatment programme for DUs. DESIGN AND METHODS: A capture-recapture method was applied for population size estimation, whereas the respondent-driven sampling (RDS) method was used to recruit a sample of DUs living in the Dakar area and determine HIV, HBV and HCV prevalence. Behavioural data were gathered during face-to-face interviews, and blood samples were collected on dried blood spots for analysis in a central laboratory. Data analysis was performed using the RDS analysis tool, and risk factors were determined by logistic regression. Access to laboratory results was organized for the participants. RESULTS: The size of the DU population in the Dakar area was estimated to reach 1324 (95% confidence interval (95% CI: 1281-1367)). Based on the 506 DUs included in the study, the HIV, HCV and HBV prevalence were 5.2% (95% CI: 3.8-6.3), 23.3% (95% CI: 21.2-25.2) and 7.9% (95% CI: 5.2-11.1), respectively. In people who inject drugs (PWID), prevalence levels increased to 9.4% for HIV and 38.9% for HCV (p=0.001 when compared to those who never injected). Women were more at risk of being HIV infected (prevalence: 13.04% versus 2.97% in males, p=0.001). Being PWID was a risk factor for HCV and HIV infection (odds ratio, OR: 2.7, 95% CI: 1.7-4.3, and OR: 4.3, 95% CI: 1.7-10.7, respectively), whereas older age and female sex were additional risk factors for HIV infection (10% increase per year of age, p=0.03 and OR: 4.9, 95% CI: 1.6-156, respectively). No specific determinant was associated with the risk of HBV infection. CONCLUSIONS: High HIV and HCV prevalence were estimated in this population of DUs (including non-injectors) living in the Dakar area, Senegal, whereas HBV prevalence was close to that of the global Senegalese population, reflecting a risk of infection independent of drug use. Women seem to be highly vulnerable and deserve targeted interventions for decreasing exposure to HIV, while behavioural risk factors for HIV and HCV include the use of unsafe injections, reflecting the urgent need for developing harm reduction interventions and access to opioid substitution therapy services.

An urgent need to scale-up injecting drug harm reduction services in Tanzania: prevalence of blood-borne viruses among drug users in Temeke District, Dar-es-Salaam, 2011.

BACKGROUND: Injecting drug use (IDU) is a growing concern in Tanzania compounded by reports of high-risk injecting and sexual risk behaviours among people who inject drugs (PWID). These behaviours have implications for transmission of blood-borne viruses, including HIV and hepatitis C (HCV). METHODS: We recruited 267 PWID (87% male) from Temeke District, Dar-es-Salaam through snowball and targeted sampling. A behavioural survey was administered alongside repeated rapid HIV and HCV antibody testing. HIV and HCV prevalence estimates with 95% confidence intervals (CIs) were calculated. RESULTS: Among PWID, 34.8% (95%CI 29.1-40.9) tested HIV positive (29.9% of males and 66.7% of females); 27.7% (95%CI 22.0-34.0) tested HCV antibody positive. Almost all (97%) participants were aware of HIV and 34% of HCV. 45% of male and 64% of female PWID reported a previous HIV test; only five (2%) PWID reported a previous HCV test. Of HIV and HCV positive tests, 73% and 99%, respectively, represented newly diagnosed infections. CONCLUSION: High prevalence of HIV and HCV were detected in this population of PWID. Rapid scale-up of targeted primary prevention and testing and treatment services for PWID in Tanzania is needed to prevent further transmission and consequent morbidities.

Drug use and HIV in West Africa: a neglected epidemic.

Injecting drug use is poorly documented in West Africa. HIV prevalence studies are still rare. Recent studies show that drug injection is on the rise. There is an urgent need to take this component of the HIV epidemic into account and to establish adapted intervention strategies.

Global epidemiology of injecting drug use and HIV among people who inject drugs: a systematic review.

BACKGROUND: Injecting drug use is an increasingly important cause of HIV transmission in most countries worldwide. Our aim was to determine the prevalence of injecting drug use among individuals aged 15-64 years, and of HIV among people who inject drugs. METHODS: We did a systematic search of peer-reviewed (Medline, EmBase, and PubMed/BioMed Central), internet, and grey literature databases; and data requests were made to UN agencies and international experts. 11 022 documents were reviewed, graded, and catalogued by the Reference Group to the UN on HIV and Injecting Drug Use. FINDINGS: Injecting drug use was identified in 148 countries; data for the extent of injecting drug use was absent for many countries in Africa, the Middle East, and Latin America. The presence of HIV infection among injectors had been reported in 120 of these countries. Prevalence estimates of injecting drug use could be ascertained for 61 countries, containing 77% of the world's total population aged 15-64 years. Extrapolated estimates suggest that 15.9 million (range 11.0-21.2 million) people might inject drugs worldwide; the largest numbers of injectors were found in China, the USA, and Russia, where mid-estimates of HIV prevalence among injectors were 12%, 16%, and 37%, respectively. HIV prevalence among injecting drug users was 20-40% in five countries and over 40% in nine. We estimate that, worldwide, about 3.0 million (range 0.8-6.6 million) people who inject drugs might be HIV positive. INTERPRETATION: The number of countries in which the injection of drugs has been reported has increased over the last decade. The high prevalence of HIV among many populations of injecting drug users represents a substantial global health challenge. However, existing data are far from adequate, in both quality and quantity, particularly in view of the increasing importance of injecting drug use as a mode of HIV transmission in many regions.

Characteristics and behaviors of ketamine users in France in 2003.

The increase in recreational use of ketamine in France led to the carrying out of a survey aimed at depicting the sociological profiles of French ketamine users, their addictive behaviors, and the characteristics relevant to the use of the substance. This survey is based upon the analysis of 250 questionnaires, 24 semi-directive interviews, and two focus groups. Data was collected between July 2002 and June 2003 among individuals who had used ketamine at least once since January 1, 2001. The respondents were mostly males with a polydrug addiction, aged about 24, with little post-secondary education and no steady job. Ketamine was generally the last substance experimented with throughout their lifetime, as of the age of 22. The article reviews the frequency of ketamine use observed in the population surveyed, as well as the routes of administration, the quantities used, the circumstances of use, the sought-after effects and those experienced, and the risks perceived by the users themselves. The data collected provides working facts to allow for the development and implementation of policies for preventing the use and abuse of ketamine among vulnerable populations.

[Effect of maintenance treatments on social life. A study with general practitioners]. / Impact des traitements de substitution aux opiacés sur la vie sociale. Une étude en médecine de ville.

The objective of this retrospective study was to describe drug maintenance treatments (DMT) in ambulatory care, and to evaluate their impact on social life. A convenience sample of 665 patients on DMT was recruited by 94 general practitioners in three geographic areas (Ile-de-France, Alsace, Aquitaine), and interviewed face to face by independent staff with a standardized questionnaire on three periods (one month before DMT, 6 months after beginning of DMT and 1 month before inclusion within the survey). Among the 665 patients, 76% were on buprenorphine, 20% on methadone, and 4% on morphine sulfate. Consumption of heroin and other psychoactive drugs was lower 6 months after DMT initiation. Patients were more likely to have relationships with people who did not have any problem with alcohol and drugs after DMT initiation than before treatment. They were also more likely to spend their free time alone after having begun DMT than before. All markers of social vulnerability evaluated through standardized questionnaires (employment, housing, social insurance, days of in-patient treatment related to drug consumption and number of condemnations) were improved after a six-month period with DMT. This research contributes to demonstrating the positive impact of DMT both on drug consumption and social life. Health professionals should include social support in their clinical practice.