Usefulness of Routine Laboratory Tests for Follow up of Patients Receiving Outpatient Parenteral Antimicrobial Therapy Run by Infectious Diseases Fellows

Background: The infectious disease society of America (IDSA) recommends routine laboratory tests for all patients receiving outpatient parenteral antimicrobial therapy (OPAT) to monitor for adverse events. There are no data to support how often patients should take monitoring laboratory tests. In addition, the relevance of different laboratory tests commonly used for OPAT follow up is not clearly known. Methods: We conducted a retrospective observational cohort study over a 7-year study interval (1 January 2014 to 31 December 2021). Clinical data were obtained to identify the risk factors associated with abnormal laboratory tests and determine if abnormal laboratory tests led to antibiotic change or hospital readmission. Results: Two hundred and forty-six patients met the inclusion criteria for this study. In our multivariate analysis, the Charlson comorbidity index (CCI) of 0–4 (aOR 0.39, 95%Cl 0.18–0.86), the use of ceftriaxone without vancomycin (aOR 0.47, 95%Cl 0.24–0.91) and an OPAT duration of 2–4 weeks (aOR 0.47, 95%Cl 0.24–0.91) were associated with a lower risk of OPAT complications. A CCI of 5 or more (aOR 2.5, 95%Cl (1.1–5.7)) and an OPAT duration of 5 or more weeks (aOR 2.7, 95% Cl 1.3–5.6) were associated with a higher risk of OPAT complications. An abnormal complete metabolic panel or vancomycin levels, but not an abnormal complete blood count, were associated with antibiotic change or readmission. Conclusion: Patients with fewer comorbidities, ceftriaxone and short OPAT durations are at lower risk for OPAT complications. These patients could be followed with less frequent laboratory monitoring.