title: The development and validation of the King's Brief Interstitial Lung Disease (K-BILD) health status questionnaire.
abstract: BACKGROUND
  Health status is impaired in patients with interstitial lung disease (ILD). There is a paucity of tools that assess health status in ILD. The objective of this study was to develop and validate the King's Brief Interstitial Lung Disease questionnaire (K-BILD), a new health status measure for patients with ILD.
  
  
  METHODS
  Patients with ILD were recruited from outpatient clinics. The development of the questionnaire consisted of three phases: item generation; item reduction, allocation to domains by factor analysis, Rasch analysis to create unidimensional scales and validation; and repeatability testing.
  
  
  RESULTS
  173 patients with ILD (49 with idiopathic pulmonary fibrosis) completed a preliminary 71-item questionnaire. 56 items were removed due to redundancy, low factor loadings or poor fit to the Rasch model. The final version of the K-BILD questionnaire consisted of 15 items and three domains (breathlessness and activities, chest symptoms and psychological). Internal consistency assessed with Cronbach's α coefficient was 0.94 for the K-BILD total score. Concurrent validity of the K-BILD questionnaire was high compared with St George's Respiratory Questionnaire (r=0.90) and moderate with lung function (vital capacity, r=0.50). The K-BILD questionnaire was repeatable over 2 weeks (n=44), with intraclass correlation coefficients for domains and total score 0.86-0.94. The K-BILD construct validity for patients with idiopathic pulmonary fibrosis was similar to that of other ILDs.
  
  
  CONCLUSIONS
  The K-BILD questionnaire is a brief, valid, self-completed health status measure for ILD. It could be used in the clinic to assess ILD from the patients' perspective.
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, Denmark Hill, London SE5 9RS, UK.
authors.forename: Amit S
authors.initials: AS
authors.lastname: Patel
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Siegert
authors.forename: Katherine
authors.initials: K
authors.lastname: Brignall
authors.forename: Patrick
authors.initials: P
authors.lastname: Gordon
authors.forename: Sophia
authors.initials: S
authors.lastname: Steer
authors.forename: Sujal R
authors.initials: SR
authors.lastname: Desai
authors.forename: Toby M
authors.initials: TM
authors.lastname: Maher
authors.forename: Elisabetta A
authors.initials: EA
authors.lastname: Renzoni
authors.forename: Athol U
authors.initials: AU
authors.lastname: Wells
authors.forename: Irene J
authors.initials: IJ
authors.lastname: Higginson
authors.forename: Surinder S
authors.initials: SS
authors.lastname: Birring
mesh_terms: D016009:Chi-Square Distribution; D005260:Female; D006304:Health Status; D006801:Humans; D008131:London; D017563:Lung Diseases, Interstitial / Q000503:physiopathology*; D008297:Male; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires