Estimating the number of people who inject drugs: a proposal to provide figures nationwide and its application to France.

Background: This article provides an original method of estimating the prevalence of injecting drug users (IDU) in France.

Method: In order to overcome legal restrictions hampering data linkage, the method relies on a single-source capture-recapture framework and makes use of individual data collected by a standardized survey conducted within treatment centres. Taking the hierarchical structure of data collection into consideration, a multilevel Zelterman regression model was used.

Results: In 2014, last year IDU were thought to be 103 800 (85 300; 130 000), prevalence of 2.6‰ (2.1; 3.2), and last month IDU 86 000 (69 200; 110 400), prevalence of 2.2‰ (1.7; 2.7). Estimates have been broken down by gender, revealing a 3 to 1 ratio of male-to-female; and age, showing young adults less prone to regular use of injection. It is thought that one IDU out of three was seen in treatment centres in 2014.

Conclusion: The number of last month IDU has remained stable when compared with the last available figures calculated in 2006. Nowadays IDU include heroin, buprenorphine, polydrug and stimulant users. This greater diversity ought to be taken into account by prevention policies, and underlines the need for perennial monitoring of IDU.