Development of a core outcome set for clinical trials targeting interventions aiming to improve adherence to appropriate polypharmacy in older people-an international consensus study

Background Medication non-adherence is prevalent in older people taking polypharmacy. Several interventions have been employed to improve adherence in this population. However, inconsistencies in outcomes have impeded comparisons of findings. Accordingly, this work aimed to develop a core outcome set (COS) for use in trials aiming to improve adherence to appropriate polypharmacy in older people.Methods A group of stakeholders, including academics, journal editors, healthcare professionals (HCPs) and public participants, evaluated 13 outcomes compiled from the literature in a Delphi study using a nine-point Likert scale ranging from 1 to 9, where higher scores (7-9) indicated critical importance and lower scores (1-3) unimportance. The resultant Delphi consensus list was discussed and voted on (yes: critical and no: unimportant) in two online nominal group technique (NGT) meetings. The NGT followed a five-stage approach: introduction, silent generation, round-robin, clarification and voting. An outcome was included if >= 80% of participants scored it critical and <= 15% scored it as unimportant.Results Of the 13 outcomes originally presented to participants, consensus was achieved to include six outcomes in the COS after the Delphi study (Round 1, n = 57; Round 2, n = 53; Round 3, n = 50, where 'n' represents participant numbers) and the NGT meetings (n = 10) comprising medication adherence across multiple medications, treatment burden, health-related quality of life (HRQoL), healthcare utilisation (HCU), adverse events and side effects (AEs and SEs) and cost-effectiveness.Conclusion This COS should be used in intervention studies focusing on improving adherence to appropriate polypharmacy in older people. Future work should identify outcome measurement instruments to be used alongside the COS.