Abstract
BackgroundChronic Obstructive Pulmonary Disease (COPD) influences different aspects of patient’s health-related quality of life (HRQL). While disease-specific HRQL instruments focus on symptoms and functional impairments, generic instruments cover a broader view on health. This study compares the generic EQ-5D-3 L and two disease-specific questionnaires (St.-George’s Respiratory Questionnaire (SGRQ-C), COPD Assessment Test (CAT)) in a comprehensive spectrum of COPD disease grades with particular attention on comorbidities and assesses the discriminative abilities of these instruments.MethodsUsing data from the baseline visit of the German COPD cohort COSYCONET, mean HRQL scores in different COPD grades were compared by linear regression models adjusting for age, sex, education, smoking status, BMI, and low vs. high number of comorbidities or a list of several self-reported comorbid conditions. Discriminative abilities of HRQL instruments to differentiate between COPD grades were assessed by standardized mean differences.ResultsIn 2,291 subjects in COPD GOLD grades 1–4 EQ-5D-3 L utility, EQ-5D VAS, SGRQ, and CAT were found able to discriminate between COPD grades, with some limitations for the EQ-5D utility in mild disease. Both generic and disease-specific HRQL instruments reflected the burden of comorbid conditions. The SGRQ showed the best discrimination between COPD grades and was less influenced by comorbidities, while EQ-5D utility put a higher weight on comorbid conditions. For all instruments, psychiatric disorders and peripheral artery disease showed the strongest negative associations with HRQL.ConclusionAll HRQL instruments considered reflect considerable impairment of HRQL in COPD patients, worsening with increasing COPD grade and number of comorbidities. Findings may support clinical assessment, choice of HRQL instrument in future studies, and parameterization of decision-analytic models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12890-016-0238-9) contains supplementary material, which is available to authorized users.
Highlights
Chronic Obstructive Pulmonary Disease (COPD) influences different aspects of patient’s health-related quality of life (HRQL)
Patients were classified as grade 1 with forced expiratory volume in 1 second (FEV1) % pred. ≥ 80, grade 2 with 50 ≤ FEV1 % pred. < 80, grade 3 with 30 ≤ FEV1 % pred. < 50 and grade 4 with FEV1 % pred. < 30, with predicted values based on reference equations from the Global Lung Initiative (GLI) [11]. 430 participants from the cohort reporting a physician-diagnosed COPD but with FEV1/forced vital capacity (FVC) ≥ 0.7 were excluded from this analysis as well as 20 participants with incomplete or missing lung function data
COPD grades were comparable in their gender distribution while they differed significantly regarding age, education, smoking status, body mass index (BMI), and the number of comorbidities
Summary
Chronic Obstructive Pulmonary Disease (COPD) influences different aspects of patient’s health-related quality of life (HRQL). While disease-specific instruments focus on symptoms and functional impairments associated with COPD, generic instruments are more widely applicable irrespective of the underlying disease [7]. They can be used to compare HRQL of diseased and healthy subjects or to compare the burden of different diseases. Some generic questionnaires are used as utility instruments e.g. for the calculation of quality-adjusted life years (QALYs) in health economic evaluations. They may be less sensitive to special problems of a certain disease than disease-specific instruments
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