Design, sampling, organising the field for a TLS survey and new developments: Coquelicot, a survey of drug users

摘要

The French ANRS-Coquelicot survey was conducted between 2004 and 2007 to follow the dynamics of the epidemic of hepatitis C among drug users (DU) in France. Having taken place in 5 cities (Lille, Strasbourg, Paris, Bordeaux, Marseilles), the survey was constituted of two parts, one epidemiological and the other socio-anthropological. The target population of this survey was both difficult to define and hard to reach, because of diversified social profiles, relations to drug use, and of the stigmatization of this practice. The studied DU population is the one that frequents specialised services, represents a sub-population having a 'problematic relationship to drugs' and is rather socially precarious. The methodology used in the epidemiological part of the study implemented a strategy of random sampling via a sampling scheme integrating the Generalized Weight Share Method (GWSM) and relies on the collection of biological data to estimate the prevalence of hepatitis C. The use of innovative methodological tools used for the first time in France (sampling plan with GWSM, biological tests) in the ANRS-Coquelicot survey has enabled to produce valid estimates of the prevalence of the HCV in the DU population, a particularly high prevalence which raises to 60%. The methodology implemented in this survey enabled a generalisation of its results to the studied target population. Using a mixed methods approach, the epidemiological data and qualitative data (in-depth interviews and ethnographical observations) were combined to enable a better understanding of the social context of risk and the meaning that the DUs gave it. The use of both quantitative and qualitative methodologies thus allowed a more sophisticated analysis of the risk factors involved in the exposure to hepatitis C among drug users in France.