title: The minimal important difference of the pulmonary functional status and dyspnea questionnaire in patients with severe chronic obstructive pulmonary disease.
abstract: BACKGROUND
  The modified version of the Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ-M) is used in patients with COPD to obtain information about their functional status. It consists of 3 components (change in activities, dyspnea and fatigue) ranging from 0 to 100 and has been shown to be responsive following pulmonary rehabilitation (PR). The interpretation of changes in PFSDQ-M score after an intervention is difficult in the absence of the minimal important difference (MID) of the PFSDQ-M. This study aims at investigating the MID of the PFSDQ-M.
  
  
  METHODS
  We enrolled 301 patients with COPD (FEV1 42 ± 15%pred) that completed the PFSDQ-M before and after a 3-month PR program (∆Chronic Respiratory Disease Questionnaire (CRDQ) +16 ± 12 points, ∆Six-minute walking distance (6MWD) +47 ± 89 m, both p < 0.001). An anchor-based approach consisted of calculating the correlation between the ∆PFSDQ-M and anchors with an established MID (∆CRDQ and ∆6MWD). Linear regression analyses were performed to predict the MID from these anchors. Secondly several distribution-based approaches (Cohen's effect size, empirical rule effect size and standard error of measurement method) were used.
  
  
  RESULTS
  Anchor-based estimates for the different PFSDQ-M-components were between -3 and -5 points based on CRDQ score and -6 (only calculated for change in activities) based on 6MWD. Using the distribution-based methods, the estimates of MID ranged from -3 to -5 points for the different components.
  
  
  CONCLUSIONS
  We concluded that the estimate of MID of the PFSDQ-M after pulmonary rehabilitation corresponds to a change of 5 points (range - 3 to -6) in each component in patients with severe COPD.
authors.forename: Eloisa M G
authors.initials: EM
authors.lastname: Regueiro
authors.forename: Chris
authors.initials: C
authors.lastname: Burtin
authors.forename: Paul
authors.initials: P
authors.lastname: Baten
authors.forename: Daniel
authors.initials: D
authors.lastname: Langer
authors.forename: Hans
authors.initials: H
authors.lastname: Van Remoortel
authors.forename: Valéria A Pires
authors.initials: VA
authors.lastname: Di Lorenzo
authors.forename: Dirceu
authors.initials: D
authors.lastname: Costa
authors.forename: Wim
authors.initials: W
authors.lastname: Janssens
authors.forename: Marc
authors.initials: M
authors.lastname: Decramer
authors.forename: Rik
authors.initials: R
authors.lastname: Gosselink
authors.forename: Thierry
authors.initials: T
authors.lastname: Troosters
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D004417:Dyspnea / Q000175:diagnosis* / Q000503:physiopathology; D005221:Fatigue / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology / Q000534:rehabilitation; D012016:Reference Values; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D011795:Surveys and Questionnaires