602 - Do These Labs Really Matter? Searching for the Benefit of Laboratory Monitoring in Outpatient Parenteral Antimicrobial Therapy (OPAT)

Background: Weekly laboratory monitoring is routinely performed for patients treated with Outpatient Parenteral Antimicrobial Therapy (OPAT). However, minimal evidence exists to guide this practice.

Methods: This was a single-center, retrospective cohort study to assess the value of laboratory monitoring in patients being treated with beta-lactam OPAT. This study included adult patients discharged from University of Utah Health (UUH) between January 1, 2018, and July 31, 2019, on beta-lactam OPAT with follow-up care with a UUH Infectious Diseases (ID) Provider. Patients discharged to a skilled nursing facility or long-term acute care hospital, or who received OPAT for a duration less than 7 days, were excluded. The primary aim was to describe how often abnormal laboratory values led to a therapy modification or documented adverse drug reaction (ADR) for patients receiving beta-lactam OPAT. Abnormal laboratory values were defined by consensus criteria for clinical significance (e.g., RIFLE criteria for kidney injury).  Therapy modification and ADR occurrence was determined by chart review for UUH ID Provider documentation.

Results: A total of 346 patients were included; two hundred seventy-four (79%) had abnormal laboratory values during OPAT. Of these, 12 patients had a modification to their OPAT due to abnormal laboratory values. The most common therapy modification due to abnormal laboratory values was a change of antibiotic (9/12). Two hundred thirteen of 274 patients (78%) with abnormal laboratory values were maintained on their OPAT regimen without a modification. Of the 67 therapy modifications observed, 55 (82%) were due to reasons other than abnormal laboratory results (Table 1).

Abnormal laboratory values meeting criteria for clinical significance and possible ADR were observed in 469 instances. Of these, 43 (9%) were considered ADRs by the ID provider (Table 2).Table 1 describes therapy modifications for patients on beta-lactam OPAT
Table 2 describes documented ADRs in the presence of abnormal labs for patients on beta-lactam OPAT


Conclusion: Weekly laboratory monitoring was associated with therapy modifications and documented ADRs in a small number of patients receiving beta-lactam agents as OPAT. This supports current guideline recommendations for laboratory monitoring, even for beta-lactam agents, which are considered relatively safe. Further investigation into the cost-effectiveness of this approach is warranted.