ObjectivesThe pathogen of community-acquired pneumonia (CAP) in children is typically uncertain during initial treatment, leading to systematic empiric antibiotic use. This study investigates if having rapid multiplex PCR results in the emergency department (ED) improves empiric treatment. MethodsOPTIPAC, a French multicentre study (2016-2018), enrolled patients consulting for CAP at the paediatric ED in 11 centres. Patients were randomised to either receive a multiplex PCR test plus usual care or usual care alone and followed for 15 days. The primary outcome was the appropriateness of initial antimicrobial management, determined by a blinded committee. ResultsOf the 499 randomised patients, 248 were tested with the multiplex PCR. Appropriateness of the antibiotic treatment was higher in the PCR group (168/245, 68.6% vs 120/249, 48.2%; RR 1.42 [1.22-1.66], P<0.0001), chiefly by reducing unnecessary antibiotics in viral pneumonia (RR 3.29 [2.20-4.90]). No adverse events were identified. ConclusionsThe multiplex PCR assay result at the ED improves paediatric CAP's antimicrobial stewardship, by both reducing antibiotic prescriptions and enhancing treatment appropriateness.