Cost effectiveness of a GP delivered medication review to reduce polypharmacy and potentially inappropriate prescribing in older patients with multimorbidity in Irish primary care : the SPPiRE cluster randomised controlled trial

Background Evidence on the cost effectiveness of deprescribing in multimorbidity is limited. Objective To investigate the cost effectiveness of a general practitioner (GP) delivered, individualised medication review to reduce polypharmacy and potentially inappropriate prescribing in older patients with multimorbidity in Irish primary care. Methods Within trial economic evaluation, from a healthcare perspective and based on a cluster randomised controlled trial with a 6 month follow up and 403 patients (208 Intervention and 195 Control) recruited between April 2017 and December 2019. Intervention GPs used the SPPiRE website which contained educational materials and a template to support a web- based individualised medication review. Control GPs delivered usual care. Incremental costs, quality adjusted life years (QALYs) generated using the EQ-5D-5L instrument, and expected cost effectiveness were estimated using multilevel model- ling and multiple imputation techniques. Uncertainty was explored using parametric, deterministic and probabilistic methods. Results On average, the SPPiRE intervention was dominant over usual care, with non-statistically significant mean cost sav- ings of €410 (95% confidence interval (CI): − 2211, 1409) and mean health gains of 0.014 QALYs (95% CI − 0.011, 0.039). At cost effectiveness threshold values of €20,000 and €45,000 per QALY, the probability of SPPiRE being cost effective was 0.993 and 0.988. Results were sensitive to missing data and data collection period. Conclusions The study observed a pattern towards dominance for the SPPiRE intervention, with high expected cost effec- tiveness. Notably, observed differences in costs and outcomes were consistent with chance, and missing data and related uncertainty was non trivial. The cost effectiveness evidence may be considered promising but equivocal