[Community-acquired pneumonia]

Given the inherent difficulty of determining the cause of community-acquired pneumonia (CAP) (an etiological diagnosis is only established in 40-60 % of cases), assessment of severity plays a key role in stratifying CAP patients arriving at the emergency department in three groups according to the need for hospitalization: outpatient, hospitalization, and the need for intensive care unit (ICU) admission. The two most common severity scales used to assess the need for hospital admission in CAP are the Pneumonia Severity Index (PSI) and CURB-65 score while ATS-IDSA 2007 criteria are specific to evaluate the need for ICU admission. Because of the possible etiological differences between the three groups, distinct etiological tests and empiric antibiotic treatments will be required in each subgroup, although a possible pneumococcal etiology should always be considered, since Streptococcus pneumoniae is the most common etiology of CAP in all three groups. Clinical status must be reassessed 48 hours after empirical antibiotic treatment is started.