Abstract

Background: Pneumonia remains a major cause of morbidity and mortality in older adults. Although C-reactive protein (CRP) and procalcitonin (PCT) have established roles in guiding pneumonia treatment, the prognostic value of their serialmeasurements in elderly patients with severe disease is less defined.

Methods: In this observational cohort study, 200 adults aged ≥ 65 years with severe community- or hospital-acquired pneumonia were enrolled. CRP and PCT levels were measured at ICU admission (Day 0) and on Days 1, 3, 5, and 7. The primary outcome was 30-day mortality. Patients were stratified into rapid-decline (> 50% reduction by Day 3) versus slower-decline groups for both biomarkers.

Results: A ≥ 50% Day-3 decline independently predicted lower 30-day mortality for both CRP (adjusted OR 0.52 [0.24–0.95],AUC 0.78, 95% CI 0.72–0.84) and PCT (adjustedOR 0.56 [0.27–1.00], AUC 0.76, 95% CI 0.69–0.82). Multivariate analysis confirmed that rapid biomarker declines significantly decreased mortality risk, even after adjusting for age, comorbidities, and Acute Physiology and Chronic Health Evaluation II scores. Integrating CRP/PCT trajectories with severity scores improved model discrimination (AUC from 0.73 to 0.82).

Conclusion: In older adults with severe pneumonia, dynamic changes in CRP and PCT provide valuable prognostic information beyond single measurements. Monitoring these biomarker trajectories may facilitate timely, individualized treatment strategies and improve clinical outcomes in this high-risk population.