Fiebre sin foco en menores de 5 años: actualización del enfoque diagnóstico basada en la evidencia

Abstract

Introduction: Fever without a source represents a frequent diagnostic challenge in pediatric emergency care, particularly in children under 5 years of age, due to the difficulty of distinguishing self-limited viral illnesses from serious bacterial infections. Clinical assessment remains fundamental; however, the incorporation of biomarkers, rapid diagnostic tests, and risk-stratification algorithms has modified the diagnostic approach to these patients. Objective: To analyze recent scientific evidence on the diagnostic criteria used in children under 5 years of age presenting with fever without a source, with emphasis on the clinical performance of biomarkers, ancillary diagnostic tests, and risk-stratification algorithms for the early identification of serious bacterial infections. Methods: A systematic literature review was conducted in accordance with PRISMA guidelines. PubMed, Scopus, SciELO, ScienceDirect, and Dialnet were searched. Studies published between 2024 and 2026, in English or Spanish, were included if they addressed fever without a source in pediatric patients under 5 years of age and evaluated diagnostic strategies, biomarkers, clinical algorithms, or ancillary diagnostic tests. Following the identification, screening, and eligibility assessment processes, 25 articles were included in the final synthesis. Results: The reviewed evidence indicates that risk-stratification algorithms, particularly PECARN and Step-by-Step, contribute to identifying patients with different probabilities of serious bacterial infection and may guide decisions regarding additional diagnostic testing and hospital management. Procalcitonin demonstrated favorable diagnostic performance compared with traditional biomarkers in the assessment of febrile infants. Likewise, rapid molecular tests may provide etiological information within a shorter timeframe, although their clinical utility should be interpreted alongside clinical assessment and the epidemiological context. Urinary tract infection was identified as one of the main bacterial infections associated with fever without a source. Conclusions: Current evidence supports an integrated approach combining clinical assessment, biomarkers, and risk-stratification algorithms to guide the diagnosis of serious bacterial infections in children with fever without a source. In Ecuador, limitations related to access to advanced biomarkers, molecular testing, and standardized clinical protocols may hinder the implementation of these strategies. Context-specific protocols and ongoing healthcare professional training are needed to promote evidence-based care and more rational antimicrobial use.