Abstract
OBJECTIVE: To evaluate the cost-effectiveness of implementing a penicillin allergy assessment pathway (PAAP) versus usual care within the NHS. DESIGN: A decision tree analysis over a 5-year time-period, informed by a randomised controlled trial (RCT) of PAAP and systematic review. Value of information analysis was also conducted to estimate the value of conducting a new trial. DATA SOURCES: Model inputs were informed by the ALABAMA RCT participants included in the primary analysis, 811 adults with penicillin allergy labels and recent antibiotic prescriptions, and data from published literature. INTERVENTIONS: Participants in the ALABAMA trial included in the primary analysis: PAAP (n=401) and usual care (n=410). PRIMARY AND SECONDARY OUTCOME MEASURES: Costs are presented in GBP (£) at 2022-2023 prices, quality-adjusted life years (QALYs), incremental cost-effectiveness ratio, incremental net monetary benefit (INMB), the probability of cost-effectiveness at the £20,000 and £30,000 per QALY threshold, and the cost effectiveness of a new follow-on trial. RESULTS: PAAP had incremental costs of £-83 (probability of cost saving 47.5%) and incremental QALYs of 0.036 (probability of positive benefits 47.5%). The INMBs (probability of cost-effectiveness) were £806 (48%) and £1167 (48%) under the decision thresholds of £20,000 and £30,000 per QALY, respectively. PAAP was more cost-effective among females, people aged >65 years, and more frequent antibiotic users. A new follow-on trial involving 1267 participants was estimated to cost £2.4 million and, by reducing uncertainty in the evidence, would avoid £19.6 million in costs of incorrect management decisions for eligible patients over the next 10 years. CONCLUSION: The PAAP was considered cost-effective, but significant uncertainty remained. Future trials with adequate power and longer follow-up are needed to determine the most cost-effective models for penicillin allergy testing. TRIAL REGISTRATION NUMBER: ISRCTN20579216.