CRP under 130 mg/L rules out the diagnosis of Legionella pneumophila serogroup 1 (URINELLA Study)

In case of pneumonia, some biological findings are suggestive for Legionnaire’s disease (LD) including C-reactive protein (CRP). A low level of CRP is predictive for negative Legionella Urinary-Antigen-Test (L-UAT). Observational retrospective study in Nord-Franche‐Comté Hospital with external validation in Besançon University Hospital, France which included all adults with L-UAT performed during January 2018 to December 2022. The objective was to determine CRP optimal threshold to predict a L-UAT negative result. URINELLA included 5051 patients (83 with positive L-UAT). CRP optimal threshold was 131.9 mg/L, with a negative predictive value (NPV) at 100