520 - Clinical Presentation and Course in Infants ≤90 Days Old With Bronchiolitis Evaluated in the Emergency Department

Publication Number: 2505.520

Son H. McLaren, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Carlos A. Camargo, MGH / Harvard University, Boston, MA, United States; Todd A. Florin, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States; Cheng-Shiun Leu, Columbia University, New York, NY, United States; Jiying Han, Columbia Univeristy Biostatistics Department, Jersey City, NJ, United States; Asuncion Mejias, St. Jude Children's Research Hospital, Memphis, TN, United States; Murad Megjhani, Columbia University Vagelos College of Physicians and Surgeons, Rego Park, NY, United States; Joseph Isler, Columbia University, New York, NY, United States; Rakesh Sahni, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Tammam Alalqum, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Giselle S.. Grassi, Columbia University Vagelos College of Physicians and Surgeons, Oyster Bay, NY, United States; Daniel Green, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Daniel Fenster, Columbia University Vagelos College of Physicians and Surgeons, scarsdale, NY, United States; Marlin Morel, Columbia University Vagelos College of Physicians and Surgeons, New York City, NY, United States; Tania Pakholok, Columbia University Vagelos College of Physicians and Surgeons, Brooklyn, NY, United States; Allison S.. Chang, The Warren Alpert Medical School of Brown University, Providence, RI, United States; Jason Kang, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Oliver Simpson, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Vanessa M. Lorenzo, NewYork-Presbyterian Morgan Stanley Children's Hospital, Bridgeport, CT, United States; Soojin Park, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, United States; Peter Dayan, Columbia University, Hastings on Hudson, NY, United States

Background: Young age is associated with increased bronchiolitis severity, although studies characterizing clinical presentation and course specifically in young infants (≤90 days) are lacking. Additionally, day of illness is often used to assess the risk of respiratory worsening, despite lack of evidence.

Objective: We aimed to (1) compare clinical presentation and duration of illness in young infants with bronchiolitis and (2) determine the association between day of illness at ED visit and respiratory deterioration.

Design/Methods: In this ongoing prospective cohort study, we enrolled young infants with bronchiolitis presenting to the ED. Infants were excluded for recent hospitalization and for home use of supplemental oxygen or respiratory support. Demographic and clinical data were collected using standardized interviews. Medical records were reviewed to identify respiratory deterioration, defined as initiation of respiratory support within 24 hours of ED presentation. Telephone follow up was conducted at 7 and 14 days. We conducted bivariable analyses to compare presenting symptoms and exam findings by age and viral etiology. A Kaplan-Meier curve was generated to estimate median duration of illness, defined as time from onset of symptoms to the last day of persistent cough; infants without cough and those with symptom onset >7 days were excluded. We used a generalized linear model to test for association between day of illness at ED visit and respiratory deterioration, controlling for age, sex, and viral etiology.

Results: From 11/2021-1/2025, 201 infants were enrolled. Median age was 52 days (IQR 35-73). Infants presented after a median of 3 days (IQR 2-4) of symptoms. The Table shows presenting symptoms and exam findings stratified by age and viral etiology. Clinician-observed apnea in ED was uncommon (n=5, 2%) but associated with younger age (p=0.01). Prevalence of fever, parent-observed apnea, or respiratory distress did not differ by age or viral etiology. Of 187 with follow-up data, the estimated median duration of illness was 14 days (IQR 13-15) and did not differ by age (p=0.09) or viral etiology (p=0.09) (Figure). Eighty-three (41%) infants developed respiratory deterioration. Day of illness, controlling for age, sex, and viral etiology, was not associated with respiratory deterioration (p=0.29; OR 1.10 [95% CI:0.93-1.30]).

Conclusion(s): Median duration of illness in young infants with bronchiolitis was 14 days, with minor differences in clinical presentation. Nearly half experienced respiratory deterioration, but no association was observed between day of illness and respiratory deterioration.

Table. Presenting symptoms, exam findings, and outcomes in young infants presenting to the emergency department with bronchiolitis
Categorical data are expressed as frequencies (%) and analyzed using Fisher or χ2 test. Continuous data are expressed as median [25%-75% IQR] and analyzed using Kruskal Wallis test. Values in bold indicate significant 2-sided p values.
*Other than for fast breathing and cough, all other symptoms refer to those present within 24 hours prior to ED presentation.
**Cohort was restricted to 144 infants who had viral testing using the Biofire 22-target respiratory pathogen testing and had a positive result for either respiratory syncytial virus (RSV), rhinovirus / enterovirus (RE), or both.

Figure. Duration of illness.
Figure. Of 188 (94%) infants who presented with cough and within 7 days of symptom onset, a Kaplan-Meier curve was generated using data from 187 (99%) infants with complete (n=185) or partial (n=2) 14-day follow up. Infants were censored at the last known follow-up date if illness was not resolved within the follow-up period. Estimated median duration of illness was 14 days (95% CI: 13-15), with 26% (n=134) still symptomatic on day 18 of illness (A). Median duration of illness did not differ by age (p=0.09) (B) or viral etiology (p=0.09) (C). *For respiratory syncytial virus (RSV) negative, rhinovirus/enterovirus (RE) positive group, no estimate for median duration is available as <50% infants had resolution of illness during the follow-up period.