Abstract
BACKGROUND: Dyspnea is a prominent symptom in asthma. The Dyspnea-12 (D-12), an instrument that quantifies breathlessness using 12 descriptors that tap the physical and affective aspects, has shown promise for the measurement of dyspnea in cardiorespiratory disease. OBJECTIVE: We report the results of a study designed to test the validity and reliability of the D-12 in a population of patients with asthma. METHODS: This cross-sectional study included 102 patients with asthma. Subjects completed the D-12, Hospital Anxiety and Depression scale, St. George's Respiratory Questionnaire (SGRQ), and Medical Research Council scale. Confirmatory factor analysis confirmed the two-component structure of the D-12 (i.e., seven items that tap the physical aspects of breathlessness and five items that tap the affective aspects). RESULTS: The D-12 subscales had excellent internal reliability (Cronbach's alpha for the "physical" score was 0.94 and the affective score was 0.95). The D-12 physical component was more strongly correlated with SGRQ Symptoms (r = 0.648), SGRQ Activities (r = 0.635) and Medical Research Council grade (r = 0.636), while the affective component was more strongly correlated with SGRQ Impacts (r = 0.765) and Hospital Anxiety and Depression scale scores (anxiety r = 0.641 and depression r = 0.602). CONCLUSION: This study supports validity of the D-12 for use in the assessment of dyspnea of patients with asthma. It assesses one of the most pertinent symptoms of asthma from two viewpoints-physical and affective.