Reliability of heroin users' reports of drug use behaviour using a 24 month timeline follow-back technique to assess the impact of the Australian heroin shortage

Background : In early 2001 Australia experienced a dramatic disruption to heroin supply. In order to investigate the impact of this phenomenon, heroin users were interviewed retrospectively to determine drug use behaviour over a two year period. Aim : To examine the reliability of the timeline follow-back (TLFB) technique in determining heroin users' patterns of drug use and related behaviours over a 24 month period. Method : 27 current heroin users were recruited through drug use services and interviewed about their drug use behaviour retrospectively using the calendar method of the TLFB. Test-retest reliability was measured over seven days. Results : Recall of regular drug use was generally reliable. Recall was poorest during January-April 2001, the peak period of the heroin shortage. Recall of criminal activity and weekly expenditure on drugs was variable, though generally poor. Recall of treatment entry and drug related health problems such as overdose was also variable. Conclusion : The 24 month TLFB did not obtain information reliable enough to examine sporadic drug use or overall changes in the patterns of drug use associated with the heroin shortage. To avoid this situation cohorts of injecting drug users need to be established as these phenomena cannot be accurately studied retrospectively.