Validation of a New Questionnaire with Generic and Disease-Specific Qualities: The Mcgill Copd Quality of Life Questionnaire
BACKGROUND: A validated health-related quality of life questionnaire in chronic obstructive pulmonary disease (COPD) with advantages of both generic- and disease-specific questionnaires is needed to capture patients’ perspectives of severity and impact of the disease. The McGill COPD questionnaire was created to include these advantages in English and French. It assesses three domains: symptoms, physical function and feelings with 29 items (12 from the 36-item Short-Form Health Survey with 17 from the previously developed COPD-specific module).OBJECTIVE: To evaluate the psychometric properties of this newly developed hybrid questionnaire in subjects with COPD.METHODS: Data from a multicentre, prospective cohort study involving four hospitals with COPD subjects undergoing pulmonary rehabilitation were used. Patient evaluations included health-related quality of life (the new McGill COPD questionnaire, the St Georges Respiratory Questionnaire and the 36-item Short-Form Health Survey) and pulmonary function tests pre-and postrehabilitation. Reliability, validity and responsiveness were tested.RESULTS: The study included 246 COPD subjects (111 females) with a mean age of 66 years, 87% ex- and 8% current smokers (mean 61 pack-years) and mean forced expiratory volume in 1 s of 1.12 L (Global initiative for chronic Obstructive Lung Disease stages: 2, 27%; 3, 33%; and 4, 37%). Missing data were <2% and floor and ceiling effects were <5%. Internal consistency (Cronbach’s alpha) was 0.68 to 0.82. Test-retest reliability (intracorrelation coefficients) ranged from 0.74 to 0.96 for the sub-scales, and 0.95 for the total score. Correlation with the St George’s Respiratory Questionnaire was moderately high (r=− 0.88 [95% CI −0.91 to −0.84]), consistent with the a priori hypothesis for convergent validity. The effect size was 0.33 (pre-postrehabilitation mean score difference = 6), suggesting a small to moderate change.CONCLUSIONS: The new McGill COPD questionnaire showed high internal consistency, test-retest reliability, validity and moderate responsiveness in COPD subjects.