A GIS-based methodology for improving needle exchange service delivery.

Background: A variety of legal, social and logistical factors can prevent individuals from accessing formal needle exchange programmes. One common solution to this problem is satellite exchange, which involves collaborating with people who already use an exchange to deliver needles and other supplies to those unable to access the exchange. While this approach can be very successful, one potential problem is that those most willing to deliver needles to their peers are often members of social networks that are already well connected with the needle exchange, leading to duplication of effort. In this paper we describe a simple and novel method for identifying groups of people who are demonstrably in need of improved access to needles, and for re-targeting efforts to meet the needs of those people. The method described was piloted at the Homeless Youth Alliance, San Francisco, USA, and further refined at Clean Needles Now, Los Angeles, USA.

Methods: People accessing needle exchange sites were asked to participate in a survey with two questions: "where were you and what time was it last time someone borrowed a needle from you?" and "where were you and what time was it last time you had to borrow a needle from someone else?" Responses were geocoded, and maps produced showing 'hotspots' where people were frequently finding themselves without needles.

Results: Satellite needle exchange was refined from an ad-hoc activity into one which focused on delivering needles to those with empirically demonstrable need. Maps produced in the process also proved valuable in discussions with local officials and other agencies about funding, as well as needle provision policy and practices.

Conclusion: We describe a method for rapidly assessing, describing, and responding to unmet and under-met need among injecting drug users. The method is particularly well-suited to organizations with extremely limited resources.