Distinct age-dependent phenotypes of abnormal liverfunction tests derived from national EmergencyDepartment data

Background: Abnormal liver function tests (LFTs) are frequently performed in Emergency Departments (EDs); however, the systematic characterization of age-dependent clinical phenotypes and pathogen associations remains limited.Purpose: Here we aimed to identify the distinct clinical presentations and pathogen-specific associations of pediatric and adult ED visits for abnormal LFTs.Methods: This retrospective cohort study analyzed 26,874 ED visits for abnormal LFTs in South Korea's National Emergency Department Information System (2019-2023).Patients were stratified into pediatric (0-18 years) and adult (19-64 years) groups.We characterized the clini cal presentations, concurrent diagnoses, temporal correlations with infectious pathogens, and metabolic comorbidity patterns.Results: The ED visits included 3,152 pediatric (11.7%) and 23,722 adult patients (88.3%).Pediatric presentations demonstrated fever-predominant profiles (47.3%), respiratory symptoms (6.4%), and infectious disease diagnoses (39.8%) as well as temporal correlations with respiratory viruses (rhinovirus, r=0.30; adenovirus, r=0.28;P<0.001).Adult presentations revealed previously unreported population-level temporal associations with enteric pathogens, including astrovirus (r=0.35),sapovirus (r=0.32),enteropathogenic Escherichia coli (r=0.38), and enterotoxigenic Escherichia coli (r=0.36,all P<0.001) coupled with infectious gastroenteritis (20.9%) and upper gastrointestinal disorders, including gastritis (18.3%).Adults demonstrated clustering of the following metabolic comorbidities: dyslipidemia (7.9%), hypertension (7.8%), and diabetes (6.0%).During the coronavirus disease 2019 pandemic, pediatric visits remained stable, whereas adult visits increased following the implementation of social distancing measures (rate ratio, 0.82; P=0.004). Conclusion:The ED presentation of abnormal LFTs results demonstrated distinct age-dependent phenotypes with divergent temporal pathogen associations.Pediatric cases reflected acute respiratory viral infections, whereas adult presentations showed novel population-level enteric pathogen associations with upper gastrointestinal disorders and clusters of metabolic comorbidities.These findings provide evidence supporting age-stratified diagnostic approaches for EDs.