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      Adjusting for COPD severity in database research: developing and validating an algorithm

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          When comparing chronic obstructive lung disease (COPD) interventions in database research, it is important to adjust for severity. Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines grade severity according to lung function. Most databases lack data on lung function. Previous database research has approximated COPD severity using demographics and healthcare utilization. This study aims to derive an algorithm for COPD severity using baseline data from a large respiratory trial (UPLIFT).


          Partial proportional odds logit models were developed for probabilities of being in GOLD stages II, III and IV. Concordance between predicted and observed stage was assessed using kappa-statistics. Models were estimated in a random selection of 2/3 of patients and validated in the remainder. The analysis was repeated in a subsample with a balanced distribution across severity stages. Univariate associations of COPD severity with the covariates were tested as well.


          More severe COPD was associated with being male and younger, having quit smoking, lower BMI, osteoporosis, hospitalizations, using certain medications, and oxygen. After adjusting for these variables, co-morbidities, previous healthcare resource use (eg, emergency room, hospitalizations) and inhaled corticosteroids, xanthines, or mucolytics were no longer independently associated with COPD severity, although they were in univariate tests. The concordance was poor (kappa = 0.151) and only slightly better in the balanced sample (kappa = 0.215).


          COPD severity cannot be reliably predicted from demographics and healthcare use. This limitation should be considered when interpreting findings from database studies, and additional research should explore other methods to account for COPD severity.

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          Most cited references 30

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          Randomised, double blind, placebo controlled study of fluticasone propionate in patients with moderate to severe chronic obstructive pulmonary disease: the ISOLDE trial.

          To determine the effect of long term inhaled corticosteroids on lung function, exacerbations, and health status in patients with moderate to severe chronic obstructive pulmonary disease. Double blind, placebo controlled study. Eighteen UK hospitals. 751 men and women aged between 40 and 75 years with mean forced expiratory volume in one second (FEV(1)) 50% of predicted normal. Inhaled fluticasone propionate 500 microgram twice daily from a metered dose inhaler or identical placebo. Efficacy measures: rate of decline in FEV(1) after the bronchodilator and in health status, frequency of exacerbations, respiratory withdrawals. Safety measures: morning serum cortisol concentration, incidence of adverse events. There was no significant difference in the annual rate of decline in FEV(1 )(P=0.16). Mean FEV(1) after bronchodilator remained significantly higher throughout the study with fluticasone propionate compared with placebo (P<0.001). Median exacerbation rate was reduced by 25% from 1.32 a year on placebo to 0.99 a year on with fluticasone propionate (P=0.026). Health status deteriorated by 3.2 units a year on placebo and 2.0 units a year on fluticasone propionate (P=0.0043). Withdrawals because of respiratory disease not related to malignancy were higher in the placebo group (25% v 19%, P=0.034). Fluticasone propionate 500 microgram twice daily did not affect the rate of decline in FEV(1) but did produce a small increase in FEV(1). Patients on fluticasone propionate had fewer exacerbations and a slower decline in health status. These improvements in clinical outcomes support the use of this treatment in patients with moderate to severe chronic obstructive pulmonary disease.
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            Global strategy for the diagnosis, management and prevention of COPD

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              Prevalence, diagnosis and relation to tobacco dependence of chronic obstructive pulmonary disease in a nationally representative population sample.

              Chronic obstructive pulmonary disease (COPD) is the fourth most common cause of death worldwide. It is caused primarily by cigarette smoking. Given its importance, it is remarkable that reliable national prevalence data are lacking for most countries. This study provides estimates of the national prevalence of COPD in England, the extent of under-detection of the disorder, and patterns of cigarette smoking, dependence, and motivation to stop smoking in those with the disease. Data from 8215 adults over the age of 35 who participated in the Health Survey for England were analysed. Information was obtained on self-reported and cotinine validated smoking status, cigarette dependence, motivation to stop smoking, COPD defined by spirometry using joint American Thoracic Society and European Respiratory Society criteria, and self-reports of diagnosis with respiratory disorders. Spirometry-defined COPD was present in 13.3% (95% CI 12.6 to 14.0) of participants, over 80% of whom reported no respiratory diagnosis. Even among people with severe or very severe COPD by spirometric assessment, only 46.8% (95% CI 39.1 to 54.6) reported any diagnosed respiratory disease. A total of 34.9% (95% CI 32.1 to 37.8) of people with spirometry-defined COPD were smokers compared with 22.4% (95% CI 21.4 to 23.4) of those without, and smoking prevalence increased with disease severity. Smokers with spirometry-defined COPD were more cigarette dependent but had no greater desire to quit than other smokers. COPD is common among adults in England and is predominantly undiagnosed. In smokers it is associated with higher degrees of cigarette dependence but not with a greater motivation to stop smoking.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                06 December 2011
                : 6
                : 669-678
                [1 ]Institute for Medical Technology Assessment, Erasmus University, Rotterdam, The Netherlands
                [2 ]Pfizer Inc, New York City, NY, USA
                [3 ]Boehringer Ingelheim International GmbH, Ingelheim am Rhein, Germany
                Author notes
                Correspondence: Lucas Goossens, Institute for Medical Technology Assessment, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands, Tel +31 10 4088582, Fax +31 10 4089081, Email goossens@
                © 2011 Goossens et al, publisher and licensee Dove Medical Press Ltd.

                This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.

                Original Research

                Respiratory medicine

                partial proportional odds logit, gold, healthcare resource use


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