title: Quantification of dyspnoea using descriptors: development and initial testing of the Dyspnoea-12.
abstract: BACKGROUND
  Dyspnoea is a debilitating and distressing symptom that is reflected in different verbal descriptors. Evidence suggests that dyspnoea, like pain perception, consists of sensory quality and affective components. The objective of this study was to develop an instrument that measures overall dyspnoea severity using descriptors that reflect its different aspects.
  
  
  METHODS
  81 dyspnoea descriptors were administered to 123 patients with chronic obstructive pulmonary disease (COPD), 129 with interstitial lung disease and 106 with chronic heart failure. These were reduced to 34 items using hierarchical methods. Rasch analysis informed decisions regarding further item removal and fit to the unidimensional model. Principal component analysis (PCA) explored the underlying structure of the final item set. Validity and reliability of the new instrument were further assessed in a separate group of 53 patients with COPD.
  
  
  RESULTS
  After removal of items with hierarchical methods (n = 47) and items that failed to fit the Rasch model (n = 22), 12 were retained. The "Dyspnoea-12" had good internal reliability (Cronbach's alpha = 0.9) and fit to the Rasch model (chi(2) p = 0.08). Items patterned into two groups called "physical"(n = 7) and "affective"(n = 5). In the separate validation study, Dyspnoea-12 correlated with the Hospital Anxiety and Depression Scale (anxiety r = 0.51; depression r = 0.44, p<0.001, respectively), 6-minute walk distance (r = -0.38, p<0.01) and MRC (Medical Research Council) grade (r = 0.48, p<0.01), and had good stability over time (intraclass correlation coefficient = 0.9, p<0.001).
  
  
  CONCLUSIONS
  Dyspnoea-12 fulfills modern psychometric requirements for measurement. It provides a global score of breathlessness severity that incorporates both "physical" and "affective" aspects, and can measure dyspnoea in a variety of diseases.
authors.affiliation: School of Nursing, Faculty of Health and Social Care, University of Salford, Greater Manchester, UK. j.yorke@salford.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Yorke
authors.forename: S H
authors.initials: SH
authors.lastname: Moosavi
authors.forename: C
authors.initials: C
authors.lastname: Shuldham
authors.forename: P W
authors.initials: PW
authors.lastname: Jones
mesh_terms: D000368:Aged; D001008:Anxiety Disorders / Q000175:diagnosis* / Q000523:psychology; D002908:Chronic Disease; D003866:Depressive Disorder / Q000175:diagnosis* / Q000523:psychology; D004185:Disability Evaluation; D004417:Dyspnea / Q000175:diagnosis* / Q000523:psychology; D004812:Epidemiologic Methods; D005260:Female; D006333:Heart Failure / Q000523:psychology; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000523:psychology; D008297:Male; D011594:Psychometrics; D029424:Pulmonary Disease, Chronic Obstructive / Q000523:psychology; D009626:Terminology as Topic