A trial of hierarchical cluster analysis of hospitalized wheezy infants and young children based on clinical factors

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. SUBJECTS AND 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. CONCLUSION: 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.