title: A clustering approach to identify severe bronchiolitis profiles in children.
abstract: Although bronchiolitis is generally considered a single disease, recent studies suggest heterogeneity. We aimed to identify severe bronchiolitis profiles using a clustering approach.
  
  
  
  We analysed data from two prospective, multicentre cohorts of children younger than 2 years hospitalised with bronchiolitis, one in the USA (2007-2010 winter seasons, n=2207) and one in Finland (2008-2010 winter seasons, n=408). Severe bronchiolitis profiles were determined by latent class analysis, classifying children based on clinical factors and viral aetiology.
  
  
  
  In the US study, four profiles were identified. Profile A (12%) was characterised by history of wheezing and eczema, wheezing at the emergency department (ED) presentation and rhinovirus infection. Profile B (36%) included children with wheezing at the ED presentation, but, in contrast to profile A, most did not have history of wheezing or eczema; this profile had the largest probability of respiratory syncytial virus infection. Profile C (34%) was the most severely ill group, with longer hospital stay and moderate-to-severe retractions. Profile D (17%) had the least severe illness, including non-wheezing children with shorter length of stay. Two of these profiles (A and D) were replicated in the Finnish cohort; a third group ('BC') included Finnish children with characteristics of profiles B and/or C in the US population.
  
  
  
  Several distinct clinical profiles (phenotypes) were identified by a clustering approach in two multicentre studies of children hospitalised for bronchiolitis. The observed heterogeneity has important implications for future research on the aetiology, management and long-term outcomes of bronchiolitis, such as future risk of childhood asthma.
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA Harvard Medical School, Boston, Massachusetts, USA Inserm, VIMA, Aging and Chronic Diseases. Epidemiological and Public Health Approaches, U1168, Villejuif, France UMR-S 1168, University Versailles St-Quentin-en-Yvelines, Montigny le Bretonneux, France.
authors.forename: Orianne
authors.initials: O
authors.lastname: Dumas
authors.affiliation: Harvard Medical School, Boston, Massachusetts, USA Department of Medicine, Boston Children's Hospital, Boston, Massachusetts, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Mansbach
authors.affiliation: Department of Pediatrics, Turku University Hospital, Turku, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Jartti
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Kohei
authors.initials: K
authors.lastname: Hasegawa
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: Ashley F
authors.initials: AF
authors.lastname: Sullivan
authors.affiliation: Departments of Molecular Virology and Microbiology, and Pediatrics, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Piedra
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Camargo
mesh_terms: D001988:Bronchiolitis / Q000150:complications* / Q000175:diagnosis*; D001990:Bronchiolitis, Viral / Q000175:diagnosis / Q000821:virology; D002675:Child, Preschool; D016000:Cluster Analysis; D015331:Cohort Studies; D004485:Eczema / Q000209:etiology*; D005260:Female; D005387:Finland; D006776:Hospitals, Pediatric; D006801:Humans; D007223:Infant; D008297:Male; D011446:Prospective Studies; D012135:Respiratory Sounds / Q000209:etiology*; D018357:Respiratory Syncytial Virus Infections / Q000150:complications; D014481:United States
keywords: Paediatric Lung Disaese; Respiratory Infection; Viral infection