Development of a Core Outcome Measurement Set for studies of community pharmacist-led medication reviews in older patients with multimorbidity and polypharmacy

Abstract Introduction A Core Outcome Set (COS) can harmonize outcome reporting. For medication review (MR) studies targeting older, multi-morbid patients with polypharmacy, a COS with seven outcomes is available: Health-related Quality of Life (HRQoL), pain relief, overuse, underuse, potentially inappropriate medications (PIMs), clinically significant drug-drug-interactions (DDIs), drug-related hospitalization. However, the lack of standardized outcome measurement is a barrier to its application. Thus, the next step is to operationalize each outcome by standardizing their measurement, resulting in a Core Outcome Measurement Set (COMS). As operationalization is setting-specific, a COMS was developed for MR studies in community pharmacies. Depending on the outcome type, the aims were to (1) identify outcome measurement instruments (OMIs), (2) define quality criteria for OMI selection, (3) refine outcome definitions, and/or (4) seek agreement on the appropriate measurement methods. Method Literature searches were conducted to identify OMIs. A group of 10 experts was assembled, with at least one expert contributing to each outcome. Throughout the study, they completed two online surveys and took part in two online workshops. Based on the type of outcome, different approaches were undertaken: (1) The experts selected the most appropriate OMIs for HRQoL and pain relief. (2) Recognizing national differences in OMIs for overuse, underuse and PIMs, experts established universal quality criteria for OMIs’ selection to be applied for studies. (3) To operationalize DDIs and drug-related hospitalization, experts refined the definitions of what to measure. (4) For drug-related hospitalization experts sought to identify the best measurement method. Results (1) The experts selected the EQ-5D-5L as most appropriate OMI for HRQoL and upon numerical and visual analogue scales for pain relief. (2) Seven quality criteria were defined for the content of OMIs on overuse, underuse, and PIMs. No thresholds were established for validity and feasibility criteria. (3) DDIs to be measured were refined as those with a 'major' severity rating. Drug-related hospitalization was refined as unplanned overnight stays; (4) measured by patients’ reporting. Conclusion By translating the existing COS into a practical measurement framework, this COMS supports more standardized and comparable MR research. Trial registration Registered on 16 August 2023 at Open Science Framework ( https://osf.io/57jfc ).