Measuring effectiveness of needle and syringe exchange programmes for prevention of HIV among injecting drug users

摘要

The effectiveness of needle and syringe exchange programmes (NSP) to prevent HIV infection among intravenous dug users (IDUs) has been discussed intensely for 20 years. A recent WHO summary of evidence for prevention of HIV transmission concludes in favour of NSP [1], as did Gibson et al. [2] in a review from 2001. In neither reviews were studies in favour of NSPs scrutinized to check if the authors' conclusions were sound. A cornerstone in both reviews was a paper by Hurley et al. [3], which has been cited 90 times [4]. Two later studies used the same design as Hurley et al. [5-7]. If these studies are not altogether scientifically rigorous, the impact on the conclusions in the World Health Organization (WHO) summary may be noticeable. These studies examine changes in seroprevalence among IDUs over time, comparing cities with and without NSP. An average increase in such seroprevalence for cities without NSP, and an average decrease in cities with NSP, were interpreted as evidence for a positive effectof NSP. However, the ecological studies did not control for two possibly important confounders: the stage of the epidemic among IDUs and the level of knowledge of the participants' HIV status. A careful reading suggests that weaknesses of the design and the measurements regarding the strength in the conclusions in favour of NSP were, perhaps, not addressed adequately in those studies.