Cost-effectiveness of a UK-based primary healthcare intervention: Improving Medicines use in People with Polypharmacy in Primary Care (IMPPP)

The prescribing of multiple medicines to one individual, or polypharmacy, is increasingly common. While the use of multiple medications by a patient is often appropriate, in some cases prescribed medicines may not have the intended benefit and may even cause harm, and it is important to understand the clinical and economic implications of polypharmacy and interventions to optimise prescribing. In the UK, most ongoing clinical management of polypharmacy takes place in primary care. We estimated the cost-effectiveness of the Improving Medicines use in People with Polypharmacy in Primary Care (IMPPP) trial from a UK NHS perspective. IMPPP was a pragmatic, open-label, two-arm cluster-randomised trial across 37 English general practices, including 1,715 patients. The intervention comprised a structured, enhanced process for delivering patient-centred polypharmacy reviews, and was compared to control arm practices delivering usual care. Costs were derived from routine electronic health records including primary and secondary care service utilisation data whilst QALYs were estimated via SF-12v2. Follow-up was assessed at 6 months compared to pre-randomisation baseline. Cost-effectiveness was assessed using multilevel modelling with bias-corrected and accelerated bootstrapping to calculate 95% confidence intervals. Additional one-way sensitivity analyses were conducted to explore uncertainty. Adjusted mean QALYs were slightly higher in the intervention group (0.629) versus control (0.624), with a non-significant difference of 0.006 (95% CI: -0.002 to 0.014). Mean adjusted costs were also higher in the intervention group (£4166 vs. £3655), with a non-significant cost difference of £511 (95% CI: -£73 to £949). The probability of cost-effectiveness at National Institute for the Health and Care Excellence’s £20,000/QALY and £30,000/QALY thresholds were 6% and 12% respectively. Complete case analysis showed a £138 NHS cost reduction (95% CI: -£652 to £376) and a QALY gain of 0.012 (95% CI: 0.004 to 0.021). Polypharmacy medication review as conducted in the IMPPP trial is not cost-effective. This probably reflects multiple factors, including clinical effectiveness outcomes and key cost outcomes being relatively insensitive to the intervention.