Evaluation of the Norwegian version of the Dyspnoea-12 questionnaire in patients with COPD

Background The Dyspnoea-12 (D-12) questionnaire is widely used and tested in patients with breathing difficulties. The objective of this study was to translate and undertake the first evaluation of the measurement properties of the Norwegian version of the D-12 in patients with chronic obstructive pulmonary disease (COPD) attending a 4-week inpatient pulmonary rehabilitation programme. Methods Confirmatory factor analysis was used to assess structural validity. Fit to the Rasch partial credit model and differential item functioning (DIF) were assessed in relation to age, sex and comorbidity. Based on a priori hypotheses, validity was assessed through comparisons with scores for the COPD Assessment Test (CAT), Hospital Anxiety and Depression Scales (HADS) and clinical variables. Results There were 203 (86%) respondents with a mean age (SD) of 65.2 (9.0) years, and 49% were female. The D-12 showed satisfactory structural validity including presence of physical and affective domains. There was acceptable fit to Rasch model including unidimensionality for the two domains, and no evidence of DIF. Correlations with scores for the CAT, HADS and clinical variables were as hypothesised and highest for domains assessing similar aspects of health. Conclusions The Norwegian version of the D-12 showed good evidence for validity and internal consistency in this group of patients with COPD, including support for two separate domains. Further testing for these measurement properties is recommended in other Norwegian patients with dyspnoea.