title: Clinically important differences in the intensity of chronic refractory breathlessness.
abstract: BACKGROUND
  Clinically important differences in chronic refractory breathlessness are ill defined but important in clinical practice and trial design.
  
  
  OBJECTIVE
  To estimate the clinical relevance of differences in breathlessness intensity using distribution and patient anchor methods.
  
  
  METHODS
  This was a retrospective data analysis from 213 datasets from four clinical trials for refractory breathlessness. Linear regression was used to explore the relationship between study effect size and change in breathlessness score (0-100mm visual analogue scale) and to estimate the change in score equivalent to small, moderate, and large effect sizes. Pooled individual blinded patient preference data from three randomized controlled trials were analyzed. The difference between the mean change in Day 4 minus baseline scores between preferred and non-preferred arms was calculated.
  
  
  RESULTS
  There was a strong relationship between change in score and effect size (P = 0.001; R(2) = 0.98). Values for small, moderate, and large effects were -5.5, -11.3, and -18.2mm. The participant preference change in score was -9mm (95% CI, -15.8, -2.1) (P = 0.008).
  
  
  CONCLUSIONS
  This larger dataset supports a clinically important difference of 10mm. Studies should be powered to detect this difference.
authors.affiliation: Palliative Medicine, Hull York Medical School, University of Hull, Hull, United Kingdom. Electronic address: miriam.johnson@hyms.ac.uk.
authors.forename: Miriam J
authors.initials: MJ
authors.lastname: Johnson
authors.forename: J Martin
authors.initials: JM
authors.lastname: Bland
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Oxberry
authors.forename: Amy P
authors.initials: AP
authors.lastname: Abernethy
authors.forename: David C
authors.initials: DC
authors.lastname: Currow
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D004417:Dyspnea / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods*; D015995:Prevalence; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
keywords: Minimal clinically important difference; breathlessness; dyspnea; opioid