Using Probability of Community-Acquired Pneumonia to Tailor Antimicrobials Among Inpatients: A Pragmatic, Randomized Trial

BACKGROUND: Respiratory illness is the most frequent reason for unnecessary antibiotic use among hospitalized adults. In randomized trials, procalcitonin and respiratory virus testing without guidance on test interpretation do not influence antibiotic decision-making. METHODS: We conducted a pragmatic, randomized, controlled trial of antimicrobial stewardship-guided test interpretation versus usual care among hospitalized adults receiving antibiotics for suspected respiratory infection with either low procalcitonin or positive respiratory virus testing at 2 hospitals. The intervention involved a templated note in the electronic health record interpreting test results in terms of the post-test probability of bacterial pneumonia and antibiotic decision-making. When probability of bacterial pneumonia was low, discontinuation of antibiotic therapy was recommended. The primary outcome was in-hospital antibiotic days of therapy. RESULTS: Between 1 November 2023 and 10 January 2025, 107 adults were enrolled, including 65% with low procalcitonin, 30% with positive respiratory virus testing, and 5% with both. The intervention decreased antibiotic use by an average of 4.1 in-hospital days of therapy (7.5 versus 11.6, P = .006). All respiratory antibiotics were discontinued within 5 days of initiation for 76% of intervention patients versus 49% with usual care (P = .004). Length of stay (5.5 days intervention versus 6.6 days usual care, P = .16) and 30-day readmission (7% intervention versus 19% usual care, P = .079) did not significantly differ between groups. CONCLUSIONS: In this proof-of-concept study, antimicrobial stewardship-guided interpretation of laboratory tests for viral infection using a simple template safely decreased unnecessary antibiotic use for hospitalized adults with community-acquired respiratory illness. Clinical Trial Registration. NCT05976581.