Syringe HIV seroprevalence and behavioural and demographic characteristics of intravenous drug users in Sydney, Australia, 1987.

The contents of needles and syringes returned by intravenous drug users to two Sydney needle and syringe exchange centres were analysed for HIV antibodies by the enzyme-linked immunosorbent assay (ELISA). Reactive and borderline samples were further tested by the Western blot method. Basic demographic and needle sharing data were also collected from the clients of the exchanges. Of a sample of 1544 returned syringes, 48 (3%) were confirmed as containing HIV-infected blood. The proportion of infected syringes at exchange 2 was 6% (33 out of 545), which was significantly greater (P less than 0.05) than the proportion of exchange 1 at 1.5% (15 out of 999). The difference in seroprevalence between the two centres may be related to the behavioural characteristics of the client populations that attended each of the exchanges. The maintenance of a low syringe HIV seroprevalence (1-1.5%) over a 7-month period at one exchange may indicate that the availability of sterile needles and syringes prevented transmission of HIV among the clients of that exchange. HIV antibody testing of the contents of used syringes is a potentially valuable method of monitoring HIV infection among intravenous drug users. In this study, syringe exchange schemes have proved to be suitable venues for investigating the demographic characteristics and risk-taking behaviours of this population.