Diagnosis of pneumococcal aetiology was associated with age ≥5 years (85.3% vs. 68.5%; p = 0.0095; Table 3), pleural effusion, a higher CRP concentration, a higher percentage of neutrophils in the peripheral blood, admission to an intensive care unit, chest tube drainage, and mechanical ventilation (data not shown). This evidence concerns the gene CRP and Pleural effusion.