Risk of venous thromboembolism in patients treated for bacterial infection in the community with outpatient parenteral antimicrobial therapy

Aim and method: The aim of this retrospective cohort study was to establish VTE incidence in patients managed through an OPAT service and assess utility of a common VTE prediction score normally used for inpatients. Consecutive episodes of OPAT between May 2009 and May 2012 were included. Patients on long-term anti-coagulants, those with an established indication for extended, outpatient VTE prophylaxis (i.e. patients referred to OPAT following hip or knee arthroplasty) were excluded. The Padua VTE Prediction Score was retrospectively applied to the cohort. The primary outcome was incidence of symptomatic VTE during or up to 90 days after completion of OPAT treatment. Results: There were 780 included patient episodes; 105 (13.5%) patients had a Padua VTE risk score > 3; no patients received pharmacological VTE prophylaxis during OPAT treatment. During or up to 90 days following OPAT, two proximal lower limb DVTs were diagnosed, giving VTE incidence of 2/780 (0.26%, 95% CI: 0.03-0.92%), and there were eight deaths of which none were suspected to be related to VTE. There was one intracranial haemorrhage associated death. Conclusion: This retrospective cohort study found a low incidence of VTE in OPAT patients, and does not support routine application of inpatient VTE prophylaxis algorithms to patients treated for infection in the community.