title: Identification of chronic rhinosinusitis phenotypes using cluster analysis.
abstract: BACKGROUND
  The pathophysiology of chronic rhinosinusitis (CRS) is not fully understood. In Europe and the United States, major subsets of CRS classification are based on the presence or absence of polyps. Although nasal polyps (NPs) are a critical factor, many other factors  also contribute to the pathogenesis of CRS. The aim of this study was to investigate diverse CRS phenotypes using cluster analysis.
  
  
  METHODS
  This was a multicenter study examining clinical data from CRS patients treated at five hospitals. The study design was a retrospective  analysis of prospectively collected data. Complete data were available for 425/496 patients. Data were subjected to k-means cluster analysis in an attempt to identify the different phenotypes involved in CRS.
  
  
  RESULTS
  CRS was divided into four clusters. Cluster 1 (n = 180)  and cluster 2 (n = 129) comprised patients with low peripheral eosinophil and mucosal eosinophil counts. However, polyp scores in cluster 2 were higher than cluster 1. Cluster 3 (n = 50) comprised patients with very high mucosal eosinophil counts but low polyp and symptom scores. Finally,  subjects in cluster 4 (n = 66) showed severe polyposis. Polyp score and mucosal eosinophil count were the strongest predictors of clustering by discriminant analysis.
  
  
  CONCLUSIONS
  The results of this study identified distinct clinical CRS phenotypes. CRS was classified into  four phenotypes based on NPs and mucosal eosinophil counts. Cutoff points for these factors were identified by tree analysis. Additional studies are needed to establish clinical significance of the phenotypes.
authors.affiliation: Department of Otorhinolaryngology, Jikei University School of Medicine, Tokyo, Japan. nakayama-t@jikei.ac.jp
authors.forename: Tsuguhisa
authors.initials: T
authors.lastname: Nakayama
authors.forename: Daiya
authors.initials: D
authors.lastname: Asaka
authors.forename: Mamoru
authors.initials: M
authors.lastname: Yoshikawa
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Okushi
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Matsuwaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Moriyama
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Otori
mesh_terms: D000328:Adult; D000368:Aged; D002452:Cell Count; D002908:Chronic Disease; D004804:Eosinophils / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009297:Nasal Mucosa / Q000473:pathology*; D009298:Nasal Polyps / Q000145:classification* / Q000209:etiology / Q000503:physiopathology; D012189:Retrospective Studies; D012220:Rhinitis / Q000145:classification* / Q000150:complications / Q000503:physiopathology; D012852:Sinusitis / Q000145:classification* / Q000150:complications / Q000503:physiopathology