The Place of Imaging and Microbiology in the Diagnosis of Pneumonia in the Elderly

Diagnosis of pneumonia in the elderly is difficult because of the poor sensitivity and specificity of clinical signs as well as images from chest radiography (RT). New diagnostic tools such as thoracic low-dose computed tomography (CT), which exposes the patient to a weak dose of irradiation, could improve diagnosis. Moreover, low-dose CT could provide additional accuracy in the etiological clarification of pneumonia in elderly people. As a first step, the investigators aim to perform a 1 year (12 months of inclusion + 3 months of follow-up) prospective study including the Divisions of Internal Medicine, Rehabilitation, Geriatrics and Radiology of the University Hospitals of Geneva. In this study, patients \>65 years old with a clinical suspicion of low respiratory tract infection (LRTI) will be included. They will be prescribed antimicrobial therapy. Both chest radiography and low-dose thoracic CT will be performed within the first 72 hours after admission, as will blood tests and a nasopharyngeal swab. The clinician's diagnosis, both before and after the results of the CT, will be compared at the end of the study to the adjudication committee's diagnostic opinion which will have access to all available clinical, laboratory and chest X-ray data and which will be considered the gold standard. At the end of the study, all the CT images will be blind-reviewed by two experts in radiology. The impact of CT scanning in the diagnosis of pneumonia will be assessed, both for its sensitivity and specificity in this population. During the first 12 months of the study, all patients will undergo a systematic nasopharyngeal swab at admission and at discharge, from which eluates will be conserved. During the next 12 months, virological and bacteriological polymerase chain reactions (PCR) will be performed, using new diagnostic tools, in order to determine the etiological diagnosis in this population and to evaluate the impact of the new tools in the management of pneumonia for