Comparison of Discriminative Properties among Disease-specific Questionnaires for Measuring Health-related Quality of Life in Patients with Chronic Obstructive Pulmonary Disease

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Abstract
Three disease-specific, health-related quality of life (HRQL) questionnaires have been introduced to assess patients with chronic obstructive pulmonary disease (COPD): the St. George's Respiratory Questionnaire (SGRQ), the Breathing Problems Questionnaire (BPQ), and the Chronic Respiratory Disease Questionnaire (CRQ). The purpose of the present study was to make comparisons between the SGRQ, the BPQ, and the CRQ in their discriminative properties, and to clarify the characteristics of each questionnaire. One hundred forty-three patients with mild to severe COPD completed pulmonary function tests, progressive cycle ergometer testing for exercise capacity, assessment of dyspnea, anxiety, and depression, and assessment of HRQL. The frequency distributions of the questionnaire scores showed that the SGRQ and the CRQ were normally distributed and that the BPQ was skewed toward low scores. Relationships between all dimensions of the three questionnaires were significant (correlation coefficients [Rs] = 0.74 to 0.86). The three questionnaires had significant but weak correlations (Rs = -0.24 to -0.36) with some physiologic variables (VC, FEV1, and DL(CO)/VA) and mild to moderate correlations with exercise capacity and assessment of dyspnea, anxiety, and depression. Stepwise multiple regression analyses revealed that the Baseline Dyspnea Index (BDI) score, anxiety by the Hospital Anxiety Depression Scale (HAD), and maximal oxygen uptake (VO2max) accounted for 61% of the variance in the SGRQ and that the BDI and anxiety of the HAD accounted for 53 and 49% of the variance in the BPQ and the CRQ, respectively. Dyspnea and psychologic status impacted the HRQL in patients with COPD. Although no substantial differences between the SGRQ, the BPQ, and the CRQ were evident in the correlations with physiologic parameters and the influential factors, the BPQ was found to be less discriminatory than the SGRQ and the CRQ in evaluating HRQL cross-sectionally.