Chest
Volume 137, Issue 4, April 2010, Pages 846-851
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Original Research
COPD
Measurement of COPD Severity Using a Survey-Based Score: Validation in a Clinically and Physiologically Characterized Cohort

https://doi.org/10.1378/chest.09-1855Get rights and content

Background

A comprehensive survey-based COPD severity score has usefulness for epidemiologic and health outcomes research. We previously developed and validated the survey-based COPD Severity Score without using lung function or other physiologic measurements. In this study, we aimed to further validate the severity score in a different COPD cohort and using a combination of patient-reported and objective physiologic measurements.

Methods

Using data from the Function, Living, Outcomes, and Work cohort study of COPD, we evaluated the concurrent and predictive validity of the COPD Severity Score among 1,202 subjects. The survey instrument is a 35-point score based on symptoms, medication and oxygen use, and prior hospitalization or intubation for COPD. Subjects were systemically assessed using structured telephone survey, spirometry, and 6-min walk testing.

Results

We found evidence to support concurrent validity of the score. Higher COPD Severity Score values were associated with poorer FEV1 (r = −0.38), FEV1% predicted (r = −0.40), Body mass, Obstruction, Dyspnea, Exercise Index (r = 0.57), and distance walked in 6 min (r = −0.43) (P < .0001 in all cases). Greater COPD severity was also related to poorer generic physical health status (r = −0.49) and disease-specific health-related quality of life (r = 0.57) (P < .0001). The score also demonstrated predictive validity. It was also associated with a greater prospective risk of acute exacerbation of COPD defined as ED visits (hazard ratio [HR], 1.31; 95% CI, 1.24-1.39), hospitalizations (HR, 1.59; 95% CI, 1.44-1.75), and either measure of hospital-based care for COPD (HR, 1.34; 95% CI, 1.26-1.41) (P < .0001 in all cases).

Conclusion

The COPD Severity Score is a valid survey-based measure of disease-specific severity, both in terms of concurrent and predictive validity. The score is a psychometrically sound instrument for use in epidemiologic and outcomes research in COPD.

Section snippets

Materials and Methods

The Function, Living, Outcomes, and Work Study of COPD is an ongoing prospective cohort study of adult members of an integrated health care delivery system with a physician's diagnosis of COPD. Recruitment methods have been previously reported in detail.8, 9, 10 We recruited a cohort of 1,202 Kaiser Permanente Medical Care Program members who were recently treated for COPD using a validated algorithm based both on health care use and pharmacy dispensing for COPD.11

At baseline assessment, we

Concurrent Validity of the COPD Severity Score

Baseline characteristics of the cohort are shown in Table 1 and the COPD Severity Score distribution is shown in Figure 1. Higher COPD Severity Score values were associated with poorer FEV1 (r = −0.38), FEV1% (r = −0.40), BODE Index (r = 0.57), and distance walked in 6 min (r = −0.43) (P < .0001 in all cases) (Table 2). The score also correlated with poorer generic health status (r = −0.49) and worse disease-specific HRQL (r = 0.57) (Table 3). In all cases, the correlations were similar in the

Discussion

In our original report of the COPD Severity Score, we indicated that the validation in a separate and larger cohort would be advantageous.5 In this analysis, based on an entirely independent COPD cohort, we now have further demonstrated the validity of the COPD Severity Score. The score has excellent concurrent validity compared with diverse measures of lung function, exercise capacity, HRQL, and functional limitation. It also has predictive validity for acute exacerbations of COPD leading to

Acknowledgments

Author contributions: Dr Eisner: contributed to designing the study, designing and performing the analysis, and writing the manuscript.

Dr Omachi: contributed to the analysis and writing the manuscript.

Dr Katz: contributed to writing the manuscript.

Dr Yelin: contributed to interpreting the data and writing the manuscript.

Dr Iribarren: contributed to designing the study and writing the manuscript.

Dr Blanc: contributed to designing the study, analyzing the data, and writing the manuscript.

References (0)

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Funding/Support: This study was funded by the National Heart, Lung, and Blood Institute [Grant R01 HL077618], National Institutes of Health and Flight Attendants Medical Research Institute, UCSF Bland Lane Center of Excellence in Secondhand Smoke. Dr Eisner was also supported by the National Heart, Lung, and Blood Institute [K24 HL 097245].

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestpubs.org/site/misc/reprints.xhtml).

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