Development and validation of a brief screening tool for over-the-counter codeine dependence

Background: Low-dose codeine is sold without a prescription in countries like the UK, Ireland, and South Africa. Due to misuse concerns, exploring pharmacy screening tools to identify those at risk and needing additional support is vital. Objectives: The study aims to develop and validate a brief screening tool that assesses the risk of codeine dependence with language appropriate for routine use in community pharmacies. Method: Scale development and validation occurred over two studies. In Study 1, scale item generation was based on structured analyses of psychosocial and pharmacy variables from frequent over-the-counter codeine consumers (N = 795). CFA was used to assess the cohesiveness of the resultant four-item Codeine Dependence Scale (CDS). ROC analyses were used to assess the performance of the CDS against risk cases identified by the Severity of Dependence Scale; identifying an optimal cut-off value of >= 2 as representing individuals at risk of codeine dependence. In Study 2, this CDS threshold was assessed against positive DSM-5 Opioid Use Disorder (OUD) cases related to codeine use assessed using the AUDADIS-IV. Results: With a cut-off score of >= 2, the CDS has sensitivity and specificity of 76% and 48%, respectively, against a DSM-5 codeine-related OUD diagnosis using the AUDADIS-IV. For identification of any codeine-related OUD (as measured by the AUDADIS-IV) 15 months after baseline, the CDS achieved an overall correct classification rate of 52%; 72% for positive cases. Conclusions: The CDS exhibits reasonable cross-sectional and longitudinal sensitivity but low specificity, partly due to its brevity. However, the inclusive nature of the CDS is not a negative for application as a screening tool in a pharmacy setting as individual CDS items represent critical conversation points with a pharmacist, regardless of the screening outcome. The non-confronting nature of CDS items make the scale a viable option for pharmacybased SBI in countries where codeine remains OTC.