Reliability of drug dependents' self-reports

Among 936 demands for treatment by drug users in Greece in 7 months in 1994, 78 subjects making at least two demands were identified by code numbers. The median time between demands was 50 days (range 2-219). The data obtained by interview at the first two demands were compared to estimate the reliability of the interview schedule of the First Treatment Demand protocol of the Pompidou Group of the Council of Europe. Subjects were 84.6% male, with a median age of 27 years (range 14-43) and median duration of use 11 years (range 2-27). The primary substance of use was mainly heroin (88.5%). The percentage of agreement between interviews was highest for lifetime history of injecting (100%), urban residence (98.7%) and mode of use of heroin (94.3%). Percentages of agreement were close to 90% for most other items of socio-demographic data and drug use history, whether or not the correct response to the item could logically change between interviews. It is concluded that reliability of the data is around 90% and short-term behaviour in this population is rather stable. Only employment status (52.9% agreement) and secondary substance of abuse (25.5%) appeared to be exceptions. It is noteworthy that HIV and hepatitis serostatuses were reported less reliably than most other items.