Ha. Pollack, Ignoring 'downstream infection' in the evaluation of harm reduction interventions for injection drug users, EUR J EPID, 17(4), 2001, pp. 391-395
Citations number
20
Categorie Soggetti
Envirnomentale Medicine & Public Health","Medical Research General Topics
Harm reduction interventions to reduce blood-borne disease incidence among
injection drug users (IDUs). A common strategy to estimate the long-term im
pact of such interventions is to examine short-term incidence changes withi
n a specific group of individuals exposed to the intervention. Such evaluat
ions may overstate or understate long-term program effectiveness, depending
upon the relationship between short-term and long-term incidence and preva
lence. This short paper uses steady-state comparisons and a standard random
-mixing model to scrutinize this evaluation approach. It shows that evaluat
ions based upon short-term incidence changes can be significantly biased. T
he size and direction of the resulting bias depends upon a simple rule. For
modest interventions, such analyses yield over-optimistic estimates of pro
gram effectiveness when steady-state disease prevalence exceeds 50% absent
intervention. When steady-state prevalence is below 50%, such analyses disp
lay the opposite bias.