Low-dose computed tomography for the diagnosis of pneumonia in elderly patients: a prospective, interventional cohort study

The diagnosis of pneumonia is challenging. Our objective was to assess whether a low-dose computed tomography (LDCT) modified the probability of diagnosing pneumonia in elderly patients. We prospectively included patients aged over 65 years, with a suspicion of pneumonia treated with antimicrobial therapy. All patients had a chest radiograph and LDCT within 72 h of inclusion. The treating clinician assessed the probability of pneumonia before and after the LDCT by using a Likert scale. An adjudication committee retrospectively rated the probability of pneumonia and was considered as reference for diagnosis. The main outcome was the difference in the clinician9s pneumonia probability estimates before and after LDCT and the proportion of modified diagnoses which matched the reference diagnosis (net reclassification improvement (NRI)). 200 patients with a median age of 84 years were included. After LDCT, the estimated probability of pneumonia changed in 90 (45%) patients: 60 (30%) were downgraded, 30 (15%) upgraded. The NRI was 8% (NRI event -6% + NRI non event 14%). LDCT modified the estimated probability of pneumonia in a substantial proportion of patients. It mostly helped to exclude a diagnosis of pneumonia and hence to reduce unnecessary antimicrobial therapy.