The Impact of a Structured Outpatient Parenteral Antimicrobial Therapy (OPAT) Programme on Quality of Care, Optimisation of Antimicrobial Use, and Healthcare Costs: A Retrospective Cohort Study

<b>Background/Objectives:</b> In 2022, Spaarne Gasthuis hospital implemented an outpatient parenteral antimicrobial therapy (OPAT) programme, including mandatory infectious disease (ID) specialist assessment and integrated structured workflow, aiming to improve quality of care, optimize antimicrobial use, and reduce healthcare costs. Our objective was to evaluate the impact of the OPAT programme on patient outcomes (IV duration, clinical response, adverse clinical outcomes, timely peripherally inserted central catheter (PICC) removal), antimicrobial stewardship parameters, and healthcare costs. <b>Methods:</b> This retrospective before-after cohort study used electronic health record data to compare patients treated with outpatient parenteral antimicrobial therapy before (2019) and after (August 2022-December 2024) OPAT programme implementation. Using linear and logistic regression analyses, the association between the independent variable (pre-OPAT vs. OPAT) and outcomes were assessed and adjusted for potential confounders (sex, age, department, primary and additional indications). Cost analysis was performed, and ID specialist-recommended therapy adjustments were evaluated. <b>Results:</b> In total, 529 patients were included: 118 in the pre-OPAT group, and 411 in the OPAT group. In 36.3% of OPAT cases, therapy was adjusted, thereby optimizing antimicrobial stewardship. The OPAT programme was associated with significantly shorter IV therapy duration of 13.97 (mean) days (95%CI -9.15--18.79; <i>p</i> < 0.001), significantly less meropenem use (<i>p</i> < 0.001), and significantly less adverse clinical outcomes (OR 0.58, 95%CI 0.37-0.92; <i>p</i> = 0.021), whereas no significant difference was found in clinical response (OR 1.22; 95%CI 0.67-2.32; <i>p</i> = 0.527). The programme led to cost savings of 3.343 EUR per patient. <b>Conclusions:</b> The OPAT programme optimized antimicrobial use and reduced IV therapy duration, adverse clinical outcomes, and healthcare costs.