OBJECTIVE: The number of children cared for in emergency departments (EDs) with medical complexity continues to rise. We sought to identify the concordance between 2 commonly used criteria of medical complexity among children presenting to a statewide sample of EDs. METHODS: We conducted a retrospective cross-sectional study of children presenting to a statewide sample of Illinois EDs between 2016 and 2021. We classified patients as having medical complexity when using 2 definitions (≥1 pediatric Complex Chronic Condition [CCC] or complex chronic disease using the Pediatric Medical Complexity Algorithm [PMCA]) and compared their overlap and clinical outcomes. RESULTS: Of 6,550,296 pediatric ED encounters, CCC criteria and PMCA criteria were met in 217,609 (3.3%) and 175,708 (2.7%) encounters, respectively. Among patients with complexity, 100,015 (34.1%) met both criteria, with moderate agreement (κ = 0.49). Children with complexity by CCC had similar rates of presentation to a pediatric hospital (16.3% vs 14.8%), admission (28.5% vs 33.7%), ICU stay (10.0% vs 10.1%), and in-hospital mortality (0.5% vs 0.5%) compared to children with complexity by PMCA. The most common visit diagnoses for children with CCCs were related to sickle cell disease with crisis (3.9%), abdominal pain (3.6%), and non-specific chest pain (2.7%). The most common diagnoses by PMCA were related to depressive disorders (4.9%), sickle cell disease with crisis (4.8%), and seizures (3.2%). CONCLUSIONS AND RELEVANCE: The CCC and PMCA criteria of multisystem complexity identified different populations, with moderate agreement. Careful selection of operational definitions is required for proper application and interpretation in clinical and health services research. American College of Emergency Physicians.

DOI 10.1002/EMP2.12950