Chest
Volume 139, Issue 6, June 2011, Pages 1388-1394
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Original Research
COPD
Characterizing and Quantifying the Symptomatic Features of COPD Exacerbations

https://doi.org/10.1378/chest.10-1240Get rights and content

Background

There is a need for a standardized, valid, and reliable instrument for quantifying exacerbations of COPD. The objective of this study was to identify symptom items that characterize COPD exacerbations to form a new patient diary for evaluating exacerbation frequency, severity, and duration.

Methods

Twenty-three symptom items identified from patient interviews were administered to 410 patients with COPD aged (mean ± SD) 65 ± 10 years with stable FEV1 of 51% predicted ± 20% predicted and 1.8 ± 1.8 exacerbations in the preceding 12 months. A total of 222 patients had a physician-diagnosed exacerbation; 188 were stable. Item-level analyses (floor and ceiling effects, criterion keying, item-total correlation) were used in the first stage of item reduction. Further reduction was conducted using Rasch model and descriptive item analyses. Exploratory factor analysis was performed on the items that survived the exclusion process.

Results

No item behaved differently between stable and exacerbation conditions. One item was removed after item-level analysis, and eight were removed following Rasch analysis. Together, the surviving 14 items met the criteria for a unidimensional measure of exacerbation severity. Internal consistency (person separation index) was excellent at 0.92. Post hoc exploratory factor analysis revealed one dominant factor, with three domains (breathlessness, cough and sputum, and chest symptoms) that accounted for 68% of the variance.

Conclusions

An exacerbation appears to be a quantitative rather than qualitative change from the stable state. This analysis identified a range of symptoms that form a unidimensional construct of overall exacerbation severity. The 14 items identified form the Exacerbations of Chronic Pulmonary Disease Tool (EXACT), a daily diary for detecting and quantifying exacerbation severity in COPD.

Section snippets

Study Design and Participant Recruitment

A total of 23 potential items were developed from a comprehensive series of interviews and qualitative analyses in patients with COPD.11 These items assessed patients' breathlessness, cough, sputum, chest discomfort, difficulty breathing, activity limitations, feelings of tiredness or weakness, sleep disturbance, and scared or worried feelings about their condition. Patients completed the diary each evening before bedtime, reflecting back on “today” and rating the severity of each attribute or

Sample

There were 222 acute patients and 188 stable patients. Their mean ± SD age was 65 ± 10 years, and 48% were men. Stable-state FEV1 was 51% predicted ± 20% predicted. Using independent sample t tests for continuous variables and χ2 tests for categorical variables, there were no significant differences between the groups on any demographic or clinical characteristics with two exceptions. The acute group reported more frequent events the previous year (2.2 ± 0.5) than the stable group (1.3 ± 1.2) (t

Discussion

This study identified a set of symptoms (14 items) that characterize an exacerbation of COPD, including breathlessness, chest tightness, chest congestion, cough, sputum production, chest discomfort, feeling weak or tired, sleep disturbance, and feeling scared or worried. No items performed differently between the stable and exacerbation conditions, and none appeared to be uniquely characteristic of an exacerbation. Sputum purulence or color—the item most expected to differ between states10—was

Acknowledgments

Author contributions: Dr Jones: contributed to the study design, data analysis, and writing of the manuscript.

Dr Chen: contributed to the data analysis and writing of the manuscript.

Dr Wilcox: contributed to the analyses, report preparation, and the development of content for the manuscript.

Dr Sethi: contributed to the study design, data analysis, and writing of the manuscript.

Dr Leidy: contributed to the study design, execution, data analyses, report preparation, and writing of the manuscript.

References (17)

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Funding/Support: The following companies have provided unrestricted funds to support the EXACT-PRO Initiative: AstraZeneca, GlaxoSmithKline, Pfizer Inc, Boehringer Ingelheim, Merck & Company, Sepracor Inc, Forest Laboratories Inc, Novartis, Schering-Plough, Adams Respiratory Therapeutics, Bayer, Atlanta AG (Nycomed), and Ortho-McNeil.

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

*

A list of study group members is available in e-Appendix 1.

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