The development of respondent-driven sampling (RDS) inference: A systematic review of the population mean and variance estimates.

Background: Respondent-driven sampling (RDS) is a successful data collection method used in hard-to-reach populations, like those experiencing or at high risk of drug dependence. Since its introduction in 1997, identifying appropriate methods for estimating population means and sampling variances has been challenging and numerous approaches have been developed for making inferences about these quantities. To guide researchers and practitioners in deciding which approach to use, this article reviews the literature on these methodological developments.

The Sociospatial Network: Risk and the Role of Place in the Transmission of Infectious Diseases.

Control of sexually transmitted infections and blood-borne pathogens is challenging due to their presence in groups exhibiting complex social interactions. In particular, sharing injection drug use equipment and selling sex (prostitution) puts people at high risk. Previous work examining the involvement of risk behaviours in social networks has suggested that social and geographic distance of persons within a group contributes to these pathogens' endemicity.

Outlier populations: individual and social network correlates of solvent-using injection drug users.

Objective: We previously identified a high prevalence of Hepatitis C (HCV) amongst solvent-using injection drug users (S-IDU) relative to other injection drug users within the same locality. Here we incorporated social network variables to better characterize some of the behavioural characteristics that may be putting this specific subgroup of IDU at elevated disease risk.

Methods: A cross-sectional survey of at-risk populations was carried out in Winnipeg, Canada in 2009.

Understanding recruitment: outcomes associated with alternate methods for seed selection in respondent driven sampling.

Background: Respondent driven sampling (RDS) was designed for sampling "hidden" populations and intended as a means of generating unbiased population estimates. Its widespread use has been accompanied by increasing scrutiny as researchers attempt to understand the extent to which the population estimates produced by RDS are, in fact, generalizable to the actual population of interest. In this study we compare two different methods of seed selection to determine whether this may influence recruitment and RDS measures.

STI phase and the geography of sexual partnerships: prevalence of long-distance sexual contacts among chlamydia, gonorrhea, and coinfected STI cases in Manitoba, Canada.

We utilized public health data and a geographic information system (ArcGIS) to study long-distance sexual partnerships (opposite and same sex partnerships) among chlamydia, gonorrhea, and coinfected STI (sexually transmitted infection) cases. The top 10% of relationships among chlamydia and gonorrhea cases and their contacts equaled or exceeded 198 km and 237 km respectively; the top 15% of partnerships among coinfected cases equaled or exceeded 207 km. This research also detected proportionately more long-distance partnerships among gonorrhea cases than among chlamydia cases.

Transmission patterns of HIV and hepatitis C virus among networks of people who inject drugs.

Background: The risk-related behaviours and practices associated with injection drug use remain a driver of HIV and hepatitis C virus (HCV) transmission throughout the world. Here we evaluated HIV and HCV transmission patterns in the context of social networks of injection drug users (IDU) recruited from a higher incidence region in order to better understand factors that contribute to ongoing transmission among IDU.

Methods: IDU recruited through a chain-referral method provided biological specimens for analysis.

Increased risk for hepatitis C associated with solvent use among Canadian Aboriginal injection drug users.

Background: Solvent abuse is a particularly serious issue affecting Aboriginal people. Here we examine the association between solvent use and socio-demographic variables, drug-related risk factors, and pathogen prevalence in Aboriginal injection drug users (IDU) in Manitoba, Canada.

Methods: Data originated from a cross-sectional survey of IDU from December 2003 to September 2004.

HIV and HCV discordant injecting partners and their association to drug equipment sharing.

Our objective was to examine the association between HIV and HCV discordant infection status and the sharing of drug equipment by injection drug users (IDUs). IDUs were recruited from syringe exchange and methadone treatment programmes in Montreal, Canada. Characteristics of participants and their injecting partners were elicited using a structured questionnaire.

Comparison of Neisseria gonorrhoeae multiantigen sequence typing and porB sequence analysis for identification of clusters of N. gonorrhoeae isolates.

porB DNA sequence analysis and Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) methods were compared for their abilities to discriminate strains and to identify epidemiologically congruent pairs of N. gonorrhoeae. Both methods provided high-level discrimination of strains.

Identifying heterogeneity among injection drug users: a cluster analysis approach.

Objectives: We used cluster analysis to subdivide a population of injection drug users and identify previously unknown behavioral heterogeneity within that population.

Methods: We applied cluster analysis techniques to data collected in a cross-sectional survey of injection drug users in Winnipeg, Manitoba. The clustering variables we used were based on receptive syringe sharing, ethnicity, and types of drugs injected.

Clusters of circulating Neisseria gonorrhoeae strains and association with antimicrobial resistance in Shanghai.

Objectives: (i) To distinguish Neisseria gonorrhoeae isolates in Shanghai by porB typing; (ii) to ascertain the congruence of porB DNA sequence typing with cases linked epidemiologically; (iii) to determine the association of specific PorB mutations with antimicrobial resistance to penicillin or tetracycline.

Methods: porB DNA sequences of 174 N. gonorrhoeae isolates, collected from 143 male patients and 31 female sexual partners in Shanghai were determined.

Social network-related risk factors for bloodborne virus infections among injection drug users receiving syringes through secondary exchange.

Secondary syringe exchange (SSE) refers to the exchange of sterile syringes between injection drug users (IDUs). To date there has been limited examination of SSE in relation to the social networks of IDUs. This study aimed to identify characteristics of drug injecting networks associated with the receipt of syringes through SSE.

The importance of social networks in their association to drug equipment sharing among injection drug users: a review.

Aim: To examine the scientific evidence regarding the association between characteristics of social networks of injection drug users (IDUs) and the sharing of drug injection equipment.

Methods: A search was performed on MEDLINE, EMBASE, BIOSIS, Current Contents, PsycINFO databases and other sources to identify published studies on social networks of IDUs. Papers were selected based on their examination of social network factors in relation to the sharing of syringes and drug preparation equipment (e.

Determinants of injection drug user (IDU) syringe sharing: the relationship between availability of syringes and risk network member characteristics in Winnipeg, Canada.

Aims: Despite the establishment of syringe exchange programmes, syringe-sharing behaviour remains common among some injection drug users (IDU). Previous studies have identified several individual- and social network-level variables associated with syringe sharing. We examine the extent to which each of these variables is related independently to this behaviour within a diverse study population.

Rethinking approaches to risk reduction for injection drug users: differences in drug type affect risk for HIV and hepatitis C virus infection through drug-injecting networks.

Objective: To identify and compare the drug-injecting network characteristics of cocaine and heroin injectors associated with a risk of HIV and hepatitis C virus (HCV).

Methods: Active injectors were recruited from syringe exchange and methadone programs. Characteristics of all participants and their social networks were elicited.

Clients of indoor commercial sex workers: heterogeneity in patronage patterns and implications for HIV and STI propagation through sexual networks.

Objectives: To determine whether "high-risk" clients occupied important sociometric positions in sexual networks of commercial sex workers and to estimate whether they were more likely to be HIV and STI infected.

Goal: To determine whether a classification of high-risk clients could be validated by network analysis.

Study Design: We used proxy data on clients collected from a cross-sectional survey of 49 indoor female sex workers.

Conducting HIV/AIDS research with indoor commercial sex workers: reaching a hidden population.

Background: Although comprising up to 80% of the commercial sex industry in Canada, indoor female sex workers (FSW) are generally not represented in research because they are a hidden population and difficult to access.

Objectives: This paper describes a community-academic partnership model that was established to gain access to, deliver outreach services to, and conduct community-based research with the indoor commercial sex industry in four cities in British Columbia.

Methods: The project employed an ongoing community consultation, peer-delivered approach to reaching this overlooked segment of the commercial sex industry.

Demographic, risk behaviour and personal network variables associated with prevalent hepatitis C, hepatitis B, and HIV infection in injection drug users in Winnipeg, Canada.

Background: Previous studies have used social network variables to improve our understanding of HIV transmission. Similar analytic approaches have not been undertaken for hepatitis C (HCV) or B (HBV), nor used to conduct comparative studies on these pathogens within a single setting.

Methods: A cross-sectional survey consisting of a questionnaire and blood sample was conducted on injection drug users in Winnipeg between December 2003 and September 2004.

Antimicrobial susceptibility and molecular determinants of quinolone resistance in Neisseria gonorrhoeae isolates from Shanghai.

Objectives: To determine the antimicrobial susceptibility of Neisseria gonorrhoeae from Shanghai and to type the quinolone resistance-determining regions (QRDRs) of ciprofloxacin-resistant isolates.

Methods: N. gonorrhoeae isolates (n = 159) were consecutively collected from male patients in Shanghai and examined for their antimicrobial susceptibilities to penicillin, tetracycline, ciprofloxacin, spectinomycin and ceftriaxone.

Sexually transmitted disease thresholds in Manitoba, Canada.

Purpose: Persistence of sexually transmitted infections (STI) in a population is due to the activities of a small proportion of the population with STI, who transmit infection on average to one or more susceptible sex partners during an infectious period. Within these groups, the average number of transmissions by infectious people to susceptible people in a closed group is measured by the reproductive number; a threshold, above which endemic infection is likely occur and below which, in the rest of the population, it is unlikely to occur. We hypothesized that people with repeated bacterial STI's and their sex partners include the theoretical core group and that they differ from singly infected noncore individuals.

Identification of networks of sexually transmitted infection: a molecular, geographic, and social network analysis.

Background: Despite widespread efforts to control it, Chlamydia trachomatis remains the most frequently diagnosed bacterial sexually transmitted infection (STI). Analysis of sexual networks has been proposed as a novel tool for control of and research into STI. In the present study, we combine molecular genotype data, analysis of geographic clusters, and sociodemographic descriptors to facilitate analysis of large sexual networks.

Prevalence and correlates of Chlamydia infection in Canadian street youth.

Purpose: To determine the prevalence and correlates of Chlamydia trachomatis in Canadian street youth.

Methods: A cross-sectional study of street youth between the ages of 15-24 years was conducted over a 9-month period in seven large urban centers across Canada. Youth were recruited through "drop-in" centers, outreach work, and mobile vans in each city.