Agreement between different recall periods in drug utilization studies

Abstract

Objective: To assess the agreement between three recall periods for self‑reported drug use using a 24‑hour recall period as reference. Methods: Participants were allocated into three groups with different recall periods of 7, 14 and 30 days and were interviewed at two different times. A 24‑hour recall questionnaire was answered during the first interview, and a questionnaire on drug use over the different recall periods tested was answered during the second interview. The agreement between the questionnaires was evaluated using percent agreement and kappa. Results: For continuous drugs, percent agreement varied between 92 and 99% and kappa varied between 0.71 and 0.97 for three periods tested. For drugs of occasional use, percent agreement varied between 63 and 81% and kappa varied between 0.27 and 0.52. The prevalence of drugs, particularly those of occasional use, increases with time. Conclusions: The high level of agreement between the three recall periods suggests that all of them are valid for the investigation of drugs of continuous use.