<p><strong>Importance: </strong>Identifying high priority pediatric conditions is important for setting a research agenda in hospital pediatrics that will benefit families, clinicians, and the health care system. However, the last such prioritization study was conducted more than a decade ago and used International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes.</p>

<p><strong>Objectives: </strong>To identify conditions that should be prioritized for comparative effectiveness research based on prevalence, cost, and variation in cost of hospitalizations using contemporary data at US children's hospitals.</p>

<p><strong>Design, Setting, and Participants: </strong>This retrospective cohort study of children with hospital encounters used data from the Pediatric Health Information System database. Children younger than 18 years with inpatient hospital encounters at 45 tertiary care US children's hospitals between January 1, 2016, and December 31, 2019, were included. Data were analyzed from March 2020 to April 2021.</p>

<p><strong>Main Outcomes and Measures: </strong>The condition-specific prevalence and total standardized cost, the corresponding prevalence and cost ranks, and the variation in standardized cost per encounter across hospitals were analyzed. The variation in cost was assessed using the number of outlier hospitals and intraclass correlation coefficient.</p>

<p><strong>Results: </strong>There were 2 882 490 inpatient hospital encounters (median [interquartile range] age, 4 [1-12] years; 1 554 024 [53.9%] boys) included. Among the 50 most prevalent and 50 most costly conditions (total, 74 conditions), 49 (66.2%) were medical, 15 (20.3%) were surgical, and 10 (13.5%) were medical/surgical. The top 10 conditions by cost accounted for $12.4 billion of $33.4 billion total costs (37.4%) and 592 815 encounters (33.8% of all encounters). Of 74 conditions, 4 conditions had an intraclass correlation coefficient (ICC) of 0.30 or higher (ie, major depressive disorder: ICC, 0.49; type 1 diabetes with complications: ICC, 0.36; diabetic ketoacidosis: ICC, 0.33; acute appendicitis without peritonitis: ICC, 0.30), and 9 conditions had an ICC higher than 0.20 (scoliosis: ICC, 0.27; hypertrophy of tonsils and adenoids: ICC, 0.26; supracondylar fracture of humerus: ICC, 0.25; cleft lip and palate: ICC, 0.24; acute appendicitis with peritonitis: ICC, 0.21). Examples of conditions high in prevalence, cost, and variation in cost included major depressive disorder (cost rank, 19; prevalence rank, 10; ICC, 0.49), scoliosis (cost rank, 6; prevalence rank, 38; ICC, 0.27), acute appendicitis with peritonitis (cost rank, 13; prevalence rank, 11; ICC, 0.21), asthma (cost rank, 10; prevalence rank, 2; ICC, 0.17), and dehydration (cost rank, 24; prevalence rank, 8; ICC, 0.18).</p>

<p><strong>Conclusions and Relevance: </strong>This cohort study found that major depressive disorder, scoliosis, acute appendicitis with peritonitis, asthma, and dehydration were high in prevalence, costs, and variation in cost. These results could help identify where future comparative effectiveness research in hospital pediatrics should be targeted to improve the care and outcomes of hospitalized children.</p>

<p><strong>BACKGROUND: </strong>Tonsillectomy is one of the most common and cumulatively expensive surgical procedures in children. We determined if substantial variation in resource use, as measured by standardised costs, exists across hospitals for performing tonsillectomy and if higher resource use is associated with better quality of care, as measured by revisits to hospital.</p>

<p><strong>METHODS: </strong>We conducted a retrospective analysis of children undergoing routine outpatient tonsillectomy between 2011 to 2017 across US children's hospitals using an administrative and billing data source. The primary outcome measures were the hospital tonsillectomy standardised cost and the 30-day revisit rate to hospital. We analysed the interhospital variation in standardised cost by determining the number of outlier hospitals in standardised cost and the intraclass correlation coefficient.</p>

<p><strong>RESULTS: </strong>131 814 children (median age 6 years, IQR: 4,9; female sex 52.5%) underwent tonsillectomy for airway obstruction (62.9%) and infection (23.9%) across 28 hospitals. The median adjusted hospital standardised cost for tonsillectomy was $2392 (IQR: $1827, $2793; range: $1166 to $4222). There was substantial interhospital variation in costs as 11 (40%) hospitals were cost outliers, and the intraclass correlation coefficient was 0.62, suggesting that 62% of the variation in cost was attributable to variation between hospitals. The median hospital revisit rate was 9.5% (IQR: 7.8, 12.1) and higher hospital costs did not correlate with lower revisit rates ( =0.03, 95% CI -0.36 to 0.41; p=0.87).</p>

<p><strong>CONCLUSIONS: </strong>There is substantial variation in hospital resource use and standardised costs for routine outpatient tonsillectomy across US children's hospitals. Higher resource use is not associated with lower revisit rates. Further study is needed to understand the practices of lower resource use hospitals who deliver high quality of care.</p>