The impact of an outpatient parenteral antibiotic therapy (OPAT) clinic for adults with cellulitis: an interrupted time series study

Emergency department (ED) patients with cellulitis requiring intravenous antibiotics may be eligible for outpatient parenteral antibiotic therapy (OPAT). The primary objective was to determine whether implementation of an OPAT clinic results in decreased hospitalizations and return ED visits for patients receiving OPAT. We conducted an interrupted time series study involving adults with cellulitis presenting to two EDs and treated with intravenous antibiotics. The intervention was the OPAT clinic, which involved follow up at 48-96 h with an infectious disease physician to determine the need for ongoing intravenous antibiotics (implemented January 1, 2014). The primary outcomes were hospital admission and return ED visits within 14 days. Secondary outcomes were treatment failure (admission after initiating OPAT) and adverse peripheral line or antibiotic events. We used an interrupted time series design with segmented regression analysis over one-year pre-intervention and one-year post-intervention. 1666 patients were included. At the end of the study period, there was a non-significant 12% absolute increase in hospital admissions (95% CI - 1.6 to 25.5%; p = 0.084) relative to what would have been expected in the absence of the intervention, but a significant 40.7% absolute reduction in return ED visits (95% CI 25.6-55.9%; p < 0.001). Treatment failure rates were < 2% and adverse events were < 6% in both groups. Implementation of an OPAT clinic significantly reduced return ED visits for cellulitis, but did not reduce hospital admission rates. An ED-to-OPAT clinic model is safe, and has a low rate of treatment failures.