The 162 participants ranged in age from 18 to 52 years (median, 23 years), with 67% of the entire sample <25 years old. The majority (84%) of the respondents were male, and 92.7% were not ethnic Estonians (82.2% were ethnic Russians, and 10.5% were members of other Russian-speaking ethnic groups). Almost all respondents (88.9%) were born in Estonia. The majority (70.4%) of participants had never been married. Close to the half of the respondents reported no monthly income (42.7%), and 6.7% earned less than the state-estimated subsistence minimum (approximately €93).
The majority of participants, 86% (139), reported using a sterile needle for injection, whereas 10.5% (17) indicated they used a shared syringe and 14.8% (24) used shared paraphernalia (such as water, cooker, or cotton). Syringe distribution was reported at a higher rate: 19.1% (31) reported giving away a used syringe, and 23.5% (38) passed along other paraphernalia.
Altogether, 289 syringes were provided by 162 participants: 1 syringe by 146 participants, 2 syringes by 9 participants, and ≥5 syringes by 5 participants. Three participants were excluded because they did not return a syringe or provide a blood sample. We used self-reports from IDUs to identify whether syringes were shared: 130 of 159 participants reported single use of the returned syringe(s).
The prevalence of HIV infection among participants was 56% (89/159). Results of serological testing for hepatitis were as follows: 85.1% (131/154) tested positive for antibodies to HBcAg, 21.3% (33/155) tested positive for HBsAg, and 96% (153/159) tested positive for antibodies to HCV.
Testing results for syringe extracts appear in . Antibodies to HIV were found most often (56.6% of syringes), followed by antibodies to HCV (52.8%), antibodies to HBcAg (29.6%), and HBsAg (19.0%). When analysis was restricted to the extracts from the 130 unshared syringes, the percentage of positive results was generally lower but not significantly different from data for shared syringes. Results from pooled extracts were not significantly different from those of single-use syringes, and no pattern in terms of higher or lower prevalence was observed.
Prevalence of markers for bloodborne viruses in returned syringes.
Sensitivity and specificity of all syringe extracts compared with blood drawn from IDUs were very good for HIV (92.1% and 88.6%, respectively) but poorer for HBV (34.4% and 86.1%, respectively, for HBsAg) and HCV (54.9% and 83.3%, respectively) (). When the analysis excluded shared syringes, the results were similar (data not shown).
Sensitivity, specificity, and positive predictive value for detection of markers of bloodborne infection, using residual material testing from returned syringes (n = 159).