Dana M. Paquette

Syringe coverage in an Australian setting: does a high level of syringe coverage moderate syringe sharing behaviour?

We examined individual-level syringe coverage among 417 people who inject drugs who were recruited from pharmacies in New South Wales in 2009. There was a U-shaped distribution of syringe coverage with many people having very high (51%) or very low (23%) coverage. Overall, two-thirds of respondents (63%) reported adequate coverage (≥100%). Respondents who had not used a needle and syringe program in the previous month were more likely to report inadequate coverage (AOR 2.25, 95% CI 1.25–4.05) as were those who reported daily or more frequent injecting (AOR 3.69, 95% CI 2.00–6.81). Inadequate syringe coverage was not independently associated with receptive needle sharing. The level of syringe coverage was high among this sample, and met targets set out by UNAIDS and other organisations. We found that inadequate syringe coverage was not independently correlated with receptive needle sharing, possibly because coverage is sufficient to diminish the relationship between syringe availability and sharing behaviours.

Respondent-Driven Sampling and the Recruitment of People with Small Injecting Networks

Respondent-driven sampling (RDS) is a form of chain-referral sampling, similar to snowball sampling, which was developed to reach hidden populations such as people who inject drugs (PWID). RDS is said to reach members of a hidden population that may not be accessible through other sampling methods. However, less attention has been paid as to whether there are segments of the population that are more likely to be missed by RDS. This study examined the ability of RDS to capture people with small injecting networks. A study of PWID, using RDS, was conducted in 2009 in Sydney, Australia. The size of participants’ injecting networks was examined by recruitment chain and wave. Participants’ injecting network characteristics were compared to those of participants from a separate pharmacy-based study. A logistic regression analysis was conducted to examine the characteristics independently associated with having small injecting networks, using the combined RDS and pharmacy-based samples. In comparison with the pharmacy-recruited participants, RDS participants were almost 80% less likely to have small injecting networks, after adjusting for other variables. RDS participants were also more likely to have their injecting networks form a larger proportion of those in their social networks, and to have acquaintances as part of their injecting networks. Compared to those with larger injecting networks, individuals with small injecting networks were equally likely to engage in receptive sharing of injecting equipment, but less likely to have had contact with prevention services. These findings suggest that those with small injecting networks are an important group to recruit, and that RDS is less likely to capture these individuals.

Respondent-Driven Sampling (RDS) of People Who Inject Drugs: Assessing RDS Assumptions and Requirements

Respondent-driven sampling (RDS) is a relatively new form of sampling hidden populations. RDS has the ability to produce valid population estimates, provided that certain assumptions are met. This study examined whether an RDS survey of people who inject drugs (PWID) conducted in South East Sydney was able to meet the assumptions and requirements necessary to produce valid population estimates. From November 2009 to March 2010, 261 participants were recruited in 16 waves. While the methods requirements and assumptions were largely met, an apparent lack of random recruitment and the low proportion of coupons returned were sources of concern. This study shows that RDS can be used successfully in Australia as a means of recruiting PWID. However, more work is needed to confirm the soundness of the assumptions on which the calculation of valid population estimates are based.

Comparison of participants from respondent-driven sampling and service-based sampling studies of people who inject drugs

Aims: Respondent-driven sampling (RDS) is increasingly being used to sample hidden populations, such as people who inject drugs (PWIDs). This study compared samples of PWID recruited from RDS and service-based sampling methods to explore whether RDS captured a less visible group of PWID that differed in their risk profile than those captured using service-based sampling. Methods: An RDS study of PWID was conducted in Sydney, Australia in 2009. RDS participants’ frequency of use of NSP and pharmacies was calculated. Population estimates were calculated for RDS participant characteristics and were compared with sample proportions from two separate studies, which recruited participants from needle and syringe programmes (NSP) and pharmacies. Findings: Only 12% of the RDS sample may not have been accessible through either an NSP or a pharmacy. RDS participants were just as risky in their injecting practices and were more likely to access HCV prevention services than participants recruited from service-based sampling methods. Conclusions: This comparison was useful in evaluating who might be missed in service-based sampling methods. Given that RDS was not able to capture a less visible group of PWID, the choice of sampling method should take into account the availability of services through which to conduct a study.