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Development and Validation of a Survey-Based COPD Severity Score^*

^* From the Department of Medicine (Drs. Eisner, Balmes, and Blanc, Ms. Trupin and Ms. Earnest), University of California, San Francisco; of and Institute for Health Policy Studies (Drs. Katz and Yelin), University of California, San Francisco, San Francisco, CA.

Correspondence to: Mark D. Eisner, MD, MPH, FCCP, University of California, San Francisco, 350 Parnassus Ave, Ste 609, San Francisco, CA 94117; e-mail: eisner{at}itsa.ucsf.edu

Objective: To develop a comprehensive disease-specific COPD severity instrument for survey-based epidemiologic research.

Study design and setting: Using a population-based sample of 383 US adults with self-reported physician-diagnosed COPD, we developed a disease-specific COPD severity instrument. The severity score was based on structured telephone interview responses and included five overall aspects of COPD severity: respiratory symptoms, systemic corticosteroid use, other COPD medication use, previous hospitalization or intubation, and home oxygen use. We evaluated concurrent validity by examining the association between the COPD severity score and three health status domains: pulmonary function, physical health-related quality of life (HRQL), and physical disability. Pulmonary function was available for a subgroup of the sample (FEV₁, n = 49; peak expiratory flow rate [PEFR], n = 93).

Results: The COPD severity score had high internal consistency reliability (Cronbach = 0.80). Among the 49 subjects with FEV₁ data, higher COPD severity scores were associated with poorer percentage of predicted FEV₁ (r = – 0.40, p = 0.005). In the 93 subjects with available PEFR measurements, greater COPD severity was also related to worse percentage of predicted PEFR (r = – 0.35, p < 0.001). Higher COPD severity scores were strongly associated with poorer physical HRQL (r = – 0.58, p < 0.0001) and greater restricted activity attributed to a respiratory condition (r = 0.59, p < 0.0001). Higher COPD severity scores were also associated with a greater risk of difficulty with activities of daily living (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.8 to 3.0) and inability to work (OR, 4.2; 95% CI, 3.0 to 5.8).

Conclusion: The COPD severity score is a reliable and valid measure of disease severity, making it a useful research tool. The severity score, which does not require pulmonary function measurement, can be used as a study outcome or to adjust for disease severity.

Key Words: chronic bronchitis • pulmonary disease, chronic obstructive • outcome assessment (health care) • pulmonary emphysema • severity of illness index

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				H. Chen, M. D. Eisner, P. P. Katz, E. H. Yelin, and P. D. Blanc Measuring Disease-Specific Quality of Life in Obstructive Airway Disease: Validation of a Modified Version of the Airways Questionnaire 20 Chest, June 1, 2006; 129(6): 1644 - 1652. [Abstract] [Full Text] [PDF]