title: Mannitol challenge for assessment of airway responsiveness, airway inflammation and inflammatory phenotype in asthma.
abstract: BACKGROUND
  Assessment of airway inflammation in asthma is becoming increasingly important, as the inflammatory phenotype underpins the treatment response.
  
  
  OBJECTIVE
  This study aimed to evaluate mannitol as a tool for assessing airway responsiveness and airway inflammation in asthma, compared with hypertonic saline.
  
  
  METHODS
  Fifty-five subjects with stable asthma completed a hypertonic (4.5%) saline challenge and a mannitol challenge at two separate visits, performed 48-72 h apart, in random order.
  
  
  RESULTS
  Induced sputum was obtained from 49 (89%) subjects during the saline challenge and 42 (76%) subjects during the mannitol challenge (P>0.05). There was a significant correlation between the greatest percentage fall in forced expiratory volume in 1 s (FEV(1)) (r=0.6, P<0.0001), the dose-response slope (r=0.73), cumulative dose (r=0.55) and PD15 (r=0.46) for mannitol and hypertonic saline. The greatest percentage fall in FEV(1) to mannitol was less in non-eosinophilic asthma. There was a lower total cell count in mannitol vs. hypertonic-saline-induced sputum. However, sputum eosinophils and neutrophils were not significantly different. Using mannitol, a higher proportion of subjects were classified as having eosinophilic asthma. There were no differences in IL-8, neutrophil elastase or matrix-metalloproteinase 9 concentrations in sputum samples induced with mannitol or hypertonic saline.
  
  
  CONCLUSIONS
  We conclude that mannitol can be used to induce good-quality sputum, useful for analysis of inflammatory mediators and for predicting the inflammatory phenotype in asthma.
authors.affiliation: Respiratory and Sleep Medicine, Hunter Medical Research Institute, John Hunter Hospital, New Lambton, NSW, Australia. lisa.wood@newcastle.edu.au
authors.forename: L G
authors.initials: LG
authors.lastname: Wood
authors.forename: H
authors.initials: H
authors.lastname: Powell
authors.forename: P G
authors.initials: PG
authors.lastname: Gibson
mesh_terms: D001249:Asthma / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007249:Inflammation / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology*; D008297:Male; D008353:Mannitol / Q000008:administration & dosage; D008875:Middle Aged; D010641:Phenotype; D011657:Pulmonary Eosinophilia / Q000175:diagnosis / Q000235:genetics / Q000276:immunology; D015203:Reproducibility of Results; D013183:Sputum / Q000276:immunology / Q000378:metabolism
chemical_list: D008353:Mannitol