Outpatient parenteral antimicrobial therapy (OPAT) versus inpatient care in the UK: a health economic assessment for six key diagnoses

Objectives To compare costs associated with different models of outpatient parenteral antimicrobial therapy (OPAT) delivery with costs of inpatient (IP) care across key infection groups managed via OPAT in the UK. Design A cost-minimisation design was used due to evidence of similarities in patient and treatment outcomes between OPAT and IP care. A bottom-up approach was undertaken for the evaluation of OPAT associated costs. The British Society of Antimicrobial Chemotherapy National Outcomes Registry System was used to determine key infection diagnoses, mean duration of treatment and most frequent antibiotics used. Setting Several OPAT delivery settings were considered and compared with IP care. Interventions OPAT models considered were OP clinic model, nurse home visits, self (or carer)-administration by a bolus intravenous, self-administration by a commercially prefilled elastomeric device, continuous intravenous infusion of piperacillin with tazobactam or flucloxacillin with elastomeric device as OP once daily and, specifically for bone and joint and diabetic foot infections, complex outpatient oral antibiotic therapies. Results Base case and a range of scenario results showed all evaluated OPAT service delivery models to be less costly than IP stay of equivalent duration. The extent of savings varied by OPAT healthcare delivery models. Estimated OPAT costs as a proportion of IP costs were estimated at 0.23-0.53 (skin and soft-tissue infections), 0.34-0.46 (complex urinary tract infections), 0.23-0.51 (orthopaedic infections), 0.24-0.42 (diabetic foot infections) 0.40-0.56 (exacerbations of bronchiectasis) and 0.25-0.42 (intra-abdominal infections). Partial or full complex oral antibiotic therapies in orthopaedic or diabetic foot infections costs were estimated to be 0.13-0.26 of IP costs. Main OPAT costs were associated with staff time and antimicrobial medications. Conclusions OPAT is a cost-effective use of National Health Service resources for the treatment of a range of infections in the UK in patients who can be safely managed in a non-IP setting.