title: [A trial of hierarchical cluster analysis of hospitalized wheezy infants and young children based on clinical factors].
abstract: BACKGROUND
  It has been estimated that there are several phenotypes constituting wheezy infants, in addition to true asthma.
  
  
  OBJECTIVE
  The aim of this study is categorized wheezy infants and young children by cluster analysis and to turn out of categorized frequency.
  
  
  METHODS
  The study included 53 subjects aged less than 2 years old who were admitted with wheezy exacerbation. Based on clinical factors, we classified these subjects into several clinical phenotypes using cluster analysis.
  
  
  RESULTS
  The following four phenotypes were identified; cluster 1: almost all were exacerbated by RSV infection without previous wheezy episodes; cluster 2: almost all were younger, males, without previous wheezy episodes, sensitized to allergens and parental asthma, who tended to be exposed to passive smoke and have no siblings; cluster 3: almost all were slightly older males with recurrent wheezy episodes who tended to be sensitized to various allergens; cluster 4: almost all were younger females with exposure to passive-smoke, whose mother or father has a history of asthma. Cluster 4 patients tended to attend a day-care center and to be exclusively breast-fed.
  
  
  CONCLUSIONS
  Although this study covers only a limited number of subjects, cluster analysis is a new and useful method of categorizing heterogeneous wheezy infants and young children. Further analysis may establish clinical classifications of these patients.
authors: Department of Pediatrics, Medical Center for Allergy and Immune diseases, Yokohama City Minato Red Cross Hospital. isozaki.ped@yokohama.jrc.or.jp
authors: Atsushi
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authors: Isozaki
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