Abstract
BackgroundThe aims of this study were: (1) to compare the discriminative ability of a disease-specific instrument, the St. George's Respiratory Questionnaire (SGRQ) to generic instruments (i.e., EQ-5D and SF-36); and (2), to evaluate the strength of associations among clinical and health-related quality of life (HRQL) measures in chronic obstructive pulmonary disease (COPD).MethodsWe analyzed data collected from 120 COPD patients in a Veterans Affairs hospital. Patients self-completed two generic HRQL measures (EQ-5D and SF-36) and the disease-specific SGRQ. The ability of the summary scores of these HRQL measures to discriminate COPD disease severity based on Global Obstructive Lung Disease (GOLD) stage was assessed using relative efficiency ratios (REs). Strength of correlation was used to further evaluate associations between clinical and HRQL measures.ResultsMean total scores for PCS-36, EQ-VAS and SGRQ were significantly lower for the more severe stages of COPD (p < 0.05). Using SGRQ total score as reference, the summary scores of the generic measures (PCS-36, MCS-36, EQ index, and EQ-VAS) all had REs of <1. SGRQ exhibited a stronger correlation with clinical measures than the generic summary scores. For instance, SGRQ was moderately correlated with FEV1 (r = 0.43), while generic summary scores had trivial levels of correlation with FEV1 (r < 0.2).ConclusionsThe SGRQ demonstrated greater ability to discriminate among different levels of severity stages of COPD than generic measures of health, suggestive that SGRQ may provide COPD studies with greater statistical power than EQ-5D and SF-36 summary scores to capture meaningful differences in clinical severity.
Highlights
The aims of this study were: (1) to compare the discriminative ability of a disease-specific instrument, the St
Mean forced expiratory volume in 1 second (FEV1), 6-minute walk test (6MWT), and Borg dyspnea scores were significantly different across Global Obstructive Lung Disease (GOLD) stage (ANOVA/ Kruskal Wallis test (KWT), p-values < 0.001), with poorer functioning observed for patients with more severe chronic obstructive pulmonary disease (COPD) (Table 2)
Activity, and impact and total St. George’s Respiratory Questionnaire (SGRQ) scores were significantly different across stages of disease, (ANOVA/KWT, all p-values < 0.001 except a p-value of 0.03 for symptom score), with activity and total scores getting worse with stage of disease
Summary
The aims of this study were: (1) to compare the discriminative ability of a disease-specific instrument, the St. George’s Respiratory Questionnaire (SGRQ) to generic instruments (i.e., EQ-5D and SF-36); and (2), to evaluate the strength of associations among clinical and health-related quality of life (HRQL) measures in chronic obstructive pulmonary disease (COPD). Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide and is associated with a high burden of illness [1], in terms of health-related quality of life (HRQL). Measures of self-reported HRQL and pulmonary function assess different aspects of the disease and provide complementary information [9,10] Both generic and disease-specific HRQL instruments are used in COPD. EQ-5D [12] and the SF-36 [13] are generic measures of health often used in studies of COPD [3,5,10,14,15]
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