Background: Although questionnaires are used frequently with patients to self-report the severity of dyspnea as related to activities of daily living, the reliability of these instruments has not been established. The two purposes of this study were to examine the test-retest reliability of three widely used dyspnea instruments and to compare dyspnea scores at different stages of disease.
Methods: At paired baseline visits, 101 stable patients with COPD were tested; at paired follow-up visits at 3 months, 89 of these patients were tested. At each visit, patients rated dyspnea with three instruments presented in random order and then performed post-bronchodilator therapy lung function tests.
Results: Patient-reported dyspnea scores and lung function were similar at baseline (interval, 6 +/- 5 days) and follow-up visits (interval, 4 +/- 2 days). Intraclass correlation coefficients at baseline and at follow-up were 0.82 and 0.82, respectively, for the modified Medical Research Council scale; 0.90 and 0.84, respectively, for the self-administered computerized versions of the baseline dyspnea index and transition dyspnea indexes; and 0.95 and 0.89 for the University of San Diego Shortness of Breath Questionnaire results. Dyspnea ratings were significantly related to the stage of disease severity based on percent predicted FEV(1) (p < 0.001).
Conclusions: Test-retest reliability was acceptable for patient-reported dyspnea scores using three clinical instruments at baseline and at the 3-month follow-up. Our results demonstrate for the first time that patient-reported dyspnea ratings are related to the stage of disease severity.