A comparison of the level of dyspnea vs disease severity in indicating the health-related quality of life of patients with COPD

STUDY OBJECTIVES: To compare categorizations of the level of dyspnea with the staging of disease severity as defined by the FEV(1) in representing how the health-related quality of life (HRQOL) is distributed in patients with COPD. DESIGN: Cross-sectional study. SETTING: Outpatient clinic at the respiratory department of a university hospital. PATIENTS: A total of 194 consecutive male patients with stable, mild-to-severe COPD. MEASUREMENTS: The score distributions for the components of the St. George's respiratory questionnaire (SGRQ) were used as disease-specific HRQOL measures, and the scores from the Medical Outcomes Study Short Form 36-item questionnaire (SF-36) were used as generic HRQOL measures. These scores were stratified according to the level of dyspnea, as defined by the Medical Research Council (MRC) dyspnea scale, and the stage of disease severity, as defined by the American Thoracic Society (ATS). Differences in the HRQOL scores among the subgroups were compared by an analysis of variance (ANOVA). Multiple pairwise comparisons were made with Fisher's least significant difference (LSD) method, with the overall alpha-level set at 0.05. RESULTS: In those groups classified according to the level of dyspnea, significant differences were observed for the scores on the SGRQ and SF-36 (ANOVA, p < 0.05). The scores for activity and impact, and the total scores of the SGRQ and all scales, except for bodily pain and general health on the SF-36, were significantly worse for patients with severe dyspnea (MRC scale grades, 3, 4, and 5, respectively) than for those with moderate dyspnea (MRC grade level, 2; Fisher's LSD method, p < 0.05). Significant differences were recognized among the different stages of disease severity with respect to the scores from all scales of the SF-36, except for bodily pain, and all scores from the SGRQ (ANOVA, p < 0.05). However, differences in the scores on the SGRQ and SF-36 between patients with ATS stage II disease (FEV(1), 35 to 49% predicted) and stage III disease (FEV(1), < 35% predicted) were not statistically significant. CONCLUSIONS: Using the SGRQ and SF-36, the HRQOL of patients with COPD was more clearly separated by the level of dyspnea than by the ATS disease staging. In addition to the ATS disease staging, categorizations based on the level of dyspnea may be useful to clinicians in terms of the HRQOL of COPD patients.