C28-13 Procalcitonin Testing and Antibiotic Duration in Patients With Severe Community-Acquired Pneumonia: A Multi-Hospital Study

Discriminating between bacterial and viral pneumonia is challenging; procalcitonin (PCT) tends to be elevated in bacterial infections and thus may inform antibiotic use. Clinically stable, afebrile patients with negative cultures may be eligible candidates for antibiotic discontinuation. We evaluated predictors of PCT testing and associations with antibiotic use in patients with severe community-acquired pneumonia (SCAP). We retrospectively reviewed electronic medical records of adults (aged ≥ 18 years) admitted with SCAP to 12 hospitals, November 2022 - March 2025. SCAP was defined using modified ATS criteria: one major or ≥ 3 minor criteria. We excluded patients with complicated CAP (e.g., pneumonia within the preceding 30 days), concurrent infection, immunocompromise, or death within 24 hours of admission. Clinical stability was based on ATS criteria (i.e., temperature <100 °F with no more than one abnormal vital sign). We compared clinical characteristics and antibiotic durations between patients who received PCT testing within 24 hours of admission versus those who did not and, among tested patients, those with low (<0.5 µg/L) versus high (≥0.5 µg/L) PCT values. Propensity score overlap weighting was used to address potential confounding. Among 1,336 patients with SCAP, 295 (22%) were clinically stable on admission and 757 (56.7%) had PCT tests. Patients with an ED diagnosis of viral pneumonia were more likely to be tested, while those with aspiration pneumonia were less likely. PCT testing was more common with heart failure, and less common in patients requiring mechanical ventilation. CURB-65 scores and clinical stability were not associated with testing. Among tested patients, 374/757 (49.4%) had low PCT values. High values were associated with greater disease severity, including clinical instability, CURB-65 scores ≥4, WBC count >11k, increased BUN, and vasopressor use. Comorbidities leading to chronic inflammation such as dialysis, diabetes, and renal failure were associated with high PCT values. PCT testing was associated with shorter antibiotic duration versus no testing (mean 6.3 vs 7 days, adjusted mean difference, -0.7 days, 95% CI: -1.11, -0.2). Low PCT values were associated with shorter antibiotic duration than high values (mean 6 vs 7.3 days, adjusted mean difference of -1.3 days, 95% CI: -2.24, -0.35) (Figure). PCT testing was performed in about half of SCAP patients but was not ordered more frequently for stable patients, even though stable patients had lower PCTs, and might be eligible for antibiotic discontinuation. Testing was associated with shorter antibiotic duration, driven by patients with low PCT values, but the effect was modest. This abstract is funded by: AHRQ