Predictive factors, microbiology and outcome of patients with parapneumonic effusion

We aimed to determine the incidence, clinical consequences and microbiological findings related to the presence of pleural effusion in community-acquired pneumonia, and to identify predictive factors for empyema/complicated parapneumonic effusion. We analysed 4,715 consecutive patients with community-acquired pneumonia from two acute care hospitals. Patients were classified into three groups: no pleural effusion, uncomplicated parapneumonic effusion and empyema/complicated parapneumonic effusion. A total of 882 (19%) patients had radiological evidence of pleural fluid, of whom 261 (30%) met criteria for empyema/complicated parapneumonic effusion. The most important event related to the presence of uncomplicated parapneumonic effusion was a longer hospital stay. Relevant clinical and microbiological consequences were associated with empyema/complicated parapneumonic effusion. Five independent baseline characteristics could predict the development of empyema/complicated parapneumonic effusion: age < 60 yrs (p = 0.012), alcoholism (p = 0.002), pleuritic pain (p = 0.002), tachycardia >100 beats·min⁻¹ (p = 0.006) and leukocytosis >15,000 mm⁻³ (p < 0.001). A higher incidence of anaerobes and Gram-positive cocci was found in this subgroup of patients. We conclude that only the development of empyema/complicated parapneumonic effusion carried relevant consequences; this condition should be suspected in the presence of some baseline characteristics and managed by using antimicrobials active against Gram-positive cocci and anaerobes.