title: Defining the minimal important difference for the visual analogue scale assessing dyspnea in patients with malignant pleural effusions.
abstract: BACKGROUND
  The minimal important difference (MID) is essential for interpreting the results of randomised controlled trials (RCTs). Despite a number of RCTs in patients with malignant pleural effusions (MPEs) which use the visual analogue scale for dyspnea (VASD) as an outcome measure, the MID has not been established.
  
  
  METHODS
  Patients with suspected MPE undergoing a pleural procedure recorded their baseline VASD and their post-procedure VASD (24 hours after the pleural drainage), and in parallel assessed their breathlessness on a 7 point Likert scale.
  
  
  RESULTS
  The mean decrease in VASD in patients with a MPE reporting a 'small but just worthwhile decrease' in their dyspnea (i.e. equivalent to the MID) was 19mm (95% CI 14-24mm). The mean drainage volume required to produce a change in VASD of 19mm was 760ml.
  
  
  CONCLUSIONS
  The mean MID for the VASD in patients with a MPE undergoing a pleural procedure is 19mm (95% CI 14-24mm). Thus choosing an improvement of 19mm in the VASD would be justifiable in the design and analysis of future MPE studies.
authors: Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit, Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom.
authors: Eleanor K
authors: EK
authors: Mishra
authors: Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit, Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom.
authors: John P
authors: JP
authors: Corcoran
authors: Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit, Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom.
authors: Robert J
authors: RJ
authors: Hallifax
authors: Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit, Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom.
authors: John
authors: J
authors: Stradling
authors: University of Bristol, Bristol, United Kingdom.
authors: Nicholas A
authors: NA
authors: Maskell
authors: Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit, Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom.
authors: Najib M
authors: NM
authors: Rahman
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D002289:Carcinoma, Non-Small-Cell Lung / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D004322:Drainage / Q000379:methods; D004417:Dyspnea / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008654:Mesothelioma / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D016066:Pleural Effusion, Malignant / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D064232:Visual Analog Scale