Validation of a Swedish version of the Cancer Dyspnea Scale

The Cancer Dyspnea Scale (CDS) is a multidimensional measure of dyspnea experience, with three subscales related to sense of effort, sense of anxiety and sense of discomfort, and a total score. In this study, we evaluated the validity and reliability of a Swedish version, the CDS-S, in 99 patients with advanced lung cancer who were not receiving curative or life-prolonging treatments. Criterion-related validity was demonstrated by significant group differences in CDS-S scores when patients were stratified by dyspnea intensity, as measured by a visual analogue scale (VAS-D). Correlations between the total CDS-S score and other dyspnea scales varied between 0.63 and 0.68. Convergent validity was shown by comparing the CDS-S subscales with conceptually related measures of physical and emotional function and discomfort, and correlations ranged from 0.34 to 0.57. The CDS-S captured the psychological dimension of dyspnea better than did the VAS-D. Internal consistency of the CDS-S scales was confirmed by Cronbach's alpha coefficients ranging from 0.81 to 0.90. The CDS-S was well received by the patients and completed in 2 minutes. This study supports the CDS as a valid and reliable instrument to measure dyspnea experience in a palliative setting, well suited for use in research as well as in clinical practice.