Validation of Clinical Practice Guidelines for Febrile Young Infants in a Changing Epidemiological Context

Background Febrile infants are at high risk of severe and invasive bacterial infections (SBI/IBI). Several clinical practice guidelines (CPGs) have been developed to identify low‐risk infants who may be managed safely without invasive testing or hospitalization. However, their applicability may vary across healthcare systems and changing epidemiologic conditions. This study aimed to evaluate the diagnostic performance of multiple CPGs for febrile infants during a period of altered respiratory virus circulation due to non‐pharmaceutical interventions (NPI) for coronavirus disease pandemic. Methods We retrospectively reviewed data of febrile infants aged 8–60 days who visited the emergency department (ED) between January 1 and December 31, 2021. Five CPGs were applied to each case, and diagnostic performance was assessed. Results Among 63 infants included, 26 (41.3%) were diagnosed with SBI, including three cases of IBI with bacteremia, and one case of possible bacterial meningitis. Across all guidelines, infants classified as criteria‐negative showed no missed SBI except under the Laboratory Risk Index Score approach. The AAP guideline showed 29.7% specificity, 100% sensitivity, and a 1.00 negative predictive value, and other CPGs demonstrated similarly high sensitivity and negative predictive value. In contrast, the Laboratory Risk Index Score showed lower sensitivity, with several SBI cases classified as low risk. Conclusions Despite differing epidemiologic conditions, existing CPGs maintained strong diagnostic performance, supporting their adaptability and usefulness for safely ruling out SBI in well‐appearing infants in real‐world practice. Nonetheless, differences in sensitivity and specificity suggest that their application should consider diagnostic safety, resource use, and local epidemiology.