A Novel Diagnostic Scoring System to Differentiate between Legionella pneumophila Pneumonia and Streptococcus pneumoniae Pneumonia

Objective We investigated a novel diagnostic scoring system to differentiate Legionella pneumophila pneumonia from Streptococcus pneumoniae pneumonia. Methods We retrospectively reviewed the clinical data of 62 patients with L. pneumophila pneumonia (L-group) and 70 patients with S. pneumoniae pneumonia (S-group). Results The serum sodium (Na) levels tended to be lower according to the severity [age, dehydration, respiratory failure, orientation disturbance, low blood pressure (A-DROP)] score in the L-group. On a multivariate analysis, we found that four factors were independent predictive markers for inclusion in the L-group: relative bradycardia [hazard ratio (HR) 5.177, 95% confidence interval (CI): 1.072-24.993, p=0.041], lactate dehydrogenase (LDH) levels ≥292 IU/L (HR 6.804, 95% CI: 1.629-28.416, p=0.009), C-reactive protein (CRP) levels ≥21 mg/dL (HR 28.073, 95% CI: 5.654-139.462, p