title: Asthma phenotypes: consistency of classification using induced sputum.
abstract: OBJECTIVE
  Asthma can be classified as eosinophilic or non-eosinophilic based on the cell profile of induced sputum. This classification can help determine whether corticosteroid treatment is indicated. We assessed the stability of these phenotypes over time and with different treatment regimens.
  
  
  METHODS
  Clinically stable, non-smoking, asthmatic adults were enrolled in one of two studies. In study one, induced sputum cell counts from 28 subjects were analysed after 4 weeks without corticosteroid treatment and after 6 week treatments with placebo, regular inhaled beta-agonist, inhaled corticosteroid, and combined beta-agonist and corticosteroid. In study two, sputum from 26 subjects with non-eosinophilic asthma was analysed after 12 weeks of placebo and after four 2-week corticosteroid washouts. Sputum with <2% eosinophils was classified as non-eosinophilic.
  
  
  RESULTS
  Sputum classification changed frequently in both studies. In study one, only one of eight participants with non-eosinophilic sputum after placebo treatment remained non-eosinophilic throughout. In study two, all of participants had at least one eosinophilic sputum sample, despite the fact that all had been non-eosinophilic at recruitment. Neutrophilic asthma was uncommon in both studies and was also inconsistent.
  
  
  CONCLUSIONS
  The phenotypic classification of asthma changes frequently. A diagnosis of non-eosinophilic asthma should not be based on a single sputum sample.
authors.affiliation: Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, UK. bob.hancox@otago.ac.nz
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hancox
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Cowan
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Aldridge
authors.forename: Jan O
authors.initials: JO
authors.lastname: Cowan
authors.forename: Rochelle
authors.initials: R
authors.lastname: Palmay
authors.forename: Avis
authors.initials: A
authors.lastname: Williamson
authors.forename: G Ian
authors.initials: GI
authors.lastname: Town
authors.forename: D Robin
authors.initials: DR
authors.lastname: Taylor
mesh_terms: D000328:Adult; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000145:classification* / Q000188:drug therapy / Q000473:pathology*; D019819:Budesonide / Q000627:therapeutic use; D004802:Eosinophilia / Q000145:classification* / Q000473:pathology*; D004804:Eosinophils / Q000473:pathology*; D005260:Female; D006801:Humans; D007958:Leukocyte Count / Q000145:classification; D008297:Male; D008875:Middle Aged; D013183:Sputum / Q000166:cytology*; D013726:Terbutaline / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D018927:Anti-Asthmatic Agents; D019819:Budesonide; D013726:Terbutaline