title: Repeatability of induced sputum measurements in moderate to severe asthma.
abstract: BACKGROUND
  Novel therapies are being developed for patients with moderate to severe asthma. These patients may have neutrophilic airway inflammation. Induced sputum is commonly used as an endpoint in clinical trials of asthma therapies. We have performed repeated induced sputum sampling in moderate to severe asthma patients to understand the variability of cell counts, including neutrophils, and performed power calculations for studies in this group of patients.
  
  
  METHODS
  Nineteen patients with moderate to severe asthma with evidence of airflow obstruction (FEV1 ≤ 80% predicted) and suboptimal control (ACQ ≥ 1) performed repeated induced sputum separated by 1 month.
  
  
  RESULTS
  The Ri of neutrophil percentage and absolute eosinophil count demonstrated good (0.61) and moderate (0.56) repeatability respectively, but there was a poor level of agreement for eosinophil percentage and absolute neutrophil counts. The within subject SD for sputum neutrophil percentage was 15.8. In cross over studies, sample sizes of n = 14 and n = 54 are required to detect changes in neutrophil percentages by 20 and 10 % respectively at 90% power.
  
  
  CONCLUSIONS
  Sputum neutrophil percentage has good reproducibility in patients with moderate to severe asthma.
authors.affiliation: University of Manchester, Medicines Evaluation Unit, The Langley Building, Southmoor Road, Manchester, M23 9QZ, UK. Electronic address: mrossall@meu.org.uk.
authors.forename: Matthew Richard William
authors.initials: MR
authors.lastname: Rossall
authors.affiliation: University of Manchester, Medicines Evaluation Unit, The Langley Building, Southmoor Road, Manchester, M23 9QZ, UK.
authors.forename: Paul Aidan
authors.initials: PA
authors.lastname: Cadden
authors.affiliation: University of Manchester, Medicines Evaluation Unit, The Langley Building, Southmoor Road, Manchester, M23 9QZ, UK.
authors.forename: Stephanie Dawn
authors.initials: SD
authors.lastname: Molphy
authors.affiliation: University of Manchester, Medicines Evaluation Unit, The Langley Building, Southmoor Road, Manchester, M23 9QZ, UK.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Plumb
authors.affiliation: University of Manchester, Medicines Evaluation Unit, The Langley Building, Southmoor Road, Manchester, M23 9QZ, UK.
authors.forename: Dave
authors.initials: D
authors.lastname: Singh
mesh_terms: D000328:Adult; D001249:Asthma / Q000378:metabolism* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D004804:Eosinophils / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D009504:Neutrophils / Q000378:metabolism*; D015203:Reproducibility of Results; D013183:Sputum / Q000378:metabolism*
keywords: Induced sputum; Neutrophils; Repeatability; Severe asthma