1135 - The PEST Approach to Choosing Antimicrobial Therapy

Background: Selecting an empiric antimicrobial regimen can be difficult for early learners and misuse of antibiotics can lead to adverse events and antimicrobial resistance. We describe here an approach to aid internal medicine interns in their clinical decision making, particularly when it comes to diagnosing and empirically treating infections.

Methods: The PEST model was created as a four-step approach to therapeutic reasoning and choosing an appropriate antimicrobial regimen for a given infectious disease syndrome (Figure 1). 
In February 2020, we conducted two independent teaching sessions for interns on the PEST approach during noon conference. We assessed pre-and post-teaching responses to five clinical vignette-based questions to assess optimal selection of antibiotics and improvement in the use therapeutic reasoning (Figure 2). Results were presented as a percentage of interns, both pre- and post-intervention, who chose an appropriate antibiotic and a percentage of interns who provided sufficient therapeutic reasoning as defined by using at least three out of the four PEST criteria.Figure 1 – The PEST Approach Model
Figure 2 – Clinical Vignette Examples


Results: Twenty-seven interns participated in the activity. At baseline, several interns had incorporated aspects of the PEST approach in their pre-teaching responses. While the teaching session improved therapeutic reasoning as defined by the PEST strategy (Figure 3), there was no appreciable difference in antibiotic selection (Figure 4). Ten interns commented on the usefulness of the approach, specifically highlighting the systematic approach to antibiotic selection.Figure 3 – Differences in Therapeutic Reasoning After PEST Teaching
Figure 4 – Choosing The Correct Antibiotic After PEST Teaching


Conclusion: Our results showed fidelity in using the PEST approach to improve therapeutic reasoning after a teaching session, but the method did little to improve antibiotic selection. Perhaps antibiotic selection requires greater clinical experience in order to provide a narrower or more optimal spectrum of coverage. Interestingly, some interns used select “PEST” concepts prior to the intervention suggesting that the PEST approach may solidify prior knowledge or clinical reasoning skills. Continued incorporation of the PEST approach using a case-based framework may solidify conceptual and practical knowledge of antimicrobial selection.