[Investigations for etiologic causes in community-acquired pneumonia in children (besides imagery)]

The aim of laboratory investigations in acute lower respiratory tract infections in children is mainly to help to differentiate bacterial from viral infections. While blood cell counts and C reactive protein have good negative predictive value and specificity. Blood cultures are at the best positive in 10% of bacterial pneumonia. Immunofluorescence bacterial antigen detection in nasopharyngeal secretions are useful for the etiological diagnosis of viral pneumonia while polymerase chain reaction technique remains at the present time too expensive to be routinely used. Bronchoalveolar lavage is only indicated in respiratory infections that resist a first line well conducted treatment.