Derivation and validation of a composite index of severity in chronic obstructive pulmonary disease: the DOSE Index.
BACKGROUND
Chronic obstructive pulmonary disease (COPD) is increasingly recognized as a multicomponent disease with systemic consequences and effects on quality of life. Single measures such as lung function provide a limited reflection of how the disease affects patients. Composite measures have the potential to account for many of the facets of COPD.


OBJECTIVE
To derive and validate a multicomponent assessment tool of COPD severity that is applicable to all patients and health care settings.


METHODS
The index was derived using data from 375 patients with COPD in primary care. Regression analysis led to a model explaining 48% of the variance in health status as measured by the Clinical COPD Questionnaire with four components: dyspnea (D), airflow obstruction (O), smoking status (S), and exacerbation frequency (E). The DOSE Index was validated in cross-sectional and longitudinal samples in various health care settings in Holland, Japan, and the United Kingdom.


RESULTS
The DOSE Index correlated with health status in all data sets. A high DOSE Index score (> or = 4) was associated with a greater risk of hospital admission (odds ratio, 8.3 [4.1-17]) or respiratory failure (odds ratio, 7.8 [3.4-18.3]). The index predicted exacerbations in the subsequent year (P < or = 0.014).


CONCLUSIONS
The DOSE Index is a simple, valid tool for assessing the severity of COPD. The index is related to a range of clinically important outcomes such as health care consumption and predicts future events.
Respiratory Research Unit, Peninsula Medical School, University of Plymouth, Devon, UK. rupert.jones@pms.ac.uk
Rupert C
RC
Jones
Gavin C
GC
Donaldson
Niels H
NH
Chavannes
Kozui
K
Kida
Maria
M
Dickson-Spillmann
Samantha
S
Harding
Jadwiga A
JA
Wedzicha
David
D
Price
Michael E
ME
Hyland
D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004417:Dyspnea / Q000209:etiology; D005260:Female; D006304:Health Status; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000175:diagnosis*; D015203:Reproducibility of Results; D012131:Respiratory Insufficiency / Q000209:etiology; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects; D011795:Surveys and Questionnaires