Comparison of pneumonia severity scoring methods in identification of severe community acquired pneumonia

Introduction: Australian antibiotic guidelines currently recommend simpler scoring methods to stratify community-acquired pneumonia (CAP) severity and guide therapy. The aim of this study was to compare these severity scoring tools with the Pneumonia Severity Index (PSI) in the identification of severe CAP. Methods: This is a retrospective study of patients admitted with a diagnosis of CAP and radiological evidence of a new pulmonary infiltrate. Pneumonia severity scoring was calculated retrospectively using PSI, SMART-COP and CORB. Severe CAP is defined by PSI Class V, SMART-COP score ≥ 5, or CORB score ≥ 2. Comparison was made between these scoring systems to identify severe CAP, and inpatient mortality was recorded. Results: A total of 211 patients were included. Inpatient mortality rates were significantly higher for severe CAP compared to non-severe CAP classified with all 3 scoring methods. SMART-COP classified significantly less patients with severe CAP compared to both PSI (14.2% vs 25.6%, p<0.001) and CORB (14.2% vs 22.7%, p=0.001). There was no difference between PSI and CORB (25.6% vs 22.7%, p=0.47), but 50% (27/54) of patients classified as severe CAP on PSI were considered non-severe with the CORB score and 43.8% (21/48) of patients classified as severe CAP on CORB score were considered non-severe on PSI. Similar misclassifications were observed between the PSI and the SMART-COP score. Conclusions: There are significant discrepancies between pneumonia severity scoring methods in the identification of severe CAP. These findings have major implications in empirical antibiotics selection, depending on the scoring method used to assess pneumonia severity.