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      Clinical Features and C-Reactive Protein as Predictors of Bacterial Exacerbations of COPD

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          Identifying predictors of bacterial and viral pathogens in sputum from patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) may help direct management.


          We used data from a trial evaluating a C-reactive protein (CRP) point of care guided approach to managing COPD exacerbations in primary care. We used regression analyses to identify baseline clinical features, including CRP value in those randomized to testing, associated with bacterial, viral or mixed infections, defined by the presence of bacterial and viral pathogens in sputum, detected by culture or polymerase chain reaction (PCR), respectively.


          Of 386 participants with baseline sputum samples, 79 (20.5%), 123 (31.9%), and 91 (23.6%) had bacterial, viral/atypical, and mixed bacterial/viral/atypical pathogens identified, respectively. Increasing sputum purulence assessed by color chart was associated with increased odds of finding bacterial and mixed (bacterial and viral/atypical) pathogens in sputum (area under the ROC curve (AUROC) for bacterial pathogens =0.739 (95% CI: 0.670, 0.808)). Elevated CRP was associated with increased odds of finding bacterial pathogens and mixed pathogens but did not significantly increase the AUROC for predicting bacterial pathogens over sputum color alone (AUROC for combination of sputum color and CRP = 0.776 (95% CI: 0.708, 0.843), p for comparison of models = 0.053). We found no association between the presence of sputum pathogens and other clinical or demographic features.


          Sputum purulence was the best predictor of sputum bacterial pathogens and mixed bacterial viral/atypical pathogens in patients with COPD exacerbations in our study. Elevated CRP was associated with bacterial pathogens but did not add to the predictive value of sputum purulence.

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          Most cited references 22

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          Relationship of sputum color to nature and outpatient management of acute exacerbations of COPD.

          To stratify COPD patients presenting with an acute exacerbation on the basis of sputum color and to relate this to the isolation and viable numbers of bacteria recovered on culture. Open, longitudinal study of sputum characteristics and acute-phase proteins. Patients presenting to primary-care physicians in the United Kingdom. Patients were followed up as outpatients in specialist clinic. One hundred twenty-one patients with acute exacerbations of COPD were assessed together with a single sputum sample on the day of presentation (89 of whom produced a satisfactory sputum sample for analysis). One hundred nine patients were assessed 2 months later when they had returned to their stable clinical state. The expectoration of green, purulent sputum was taken as the primary indication for antibiotic therapy, whereas white or clear sputum was not considered representative of a bacterial episode and the need for antibiotic therapy. A positive bacterial culture was obtained from 84% of patients sputum if it was purulent on presentation compared with only 38% if it was mucoid (p < 0.0001). When restudied in the stable clinical state, the incidence of a positive bacterial culture was similar for both groups (38% and 41%, respectively). C-reactive protein concentrations were significantly raised (p < 0.0001) if the sputum was purulent (median, 4.5 mg/L; interquartile range [IQR], 6. 2 to 35.8). In the stable clinical state, sputum color improved significantly in the group who presented with purulent sputum from a median color number of 4.0 (IQR, 4.0 to 5.0) to 3.0 (IQR, 2.0 to 4. 0; p < 0.0001), and this was associated with a fall in median C-reactive protein level to 2.7 mg/L (IQR, 1.0 to 6.6; p < 0.0001). The presence of green (purulent) sputum was 94.4% sensitive and 77.0% specific for the yield of a high bacterial load and indicates a clear subset of patient episodes identified at presentation that is likely to benefit most from antibiotic therapy. All patients who produced white (mucoid) sputum during the acute exacerbation improved without antibiotic therapy, and sputum characteristics remained the same even when the patients had returned to their stable clinical state.
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            Impact of exacerbations on COPD.

             A Anzueto (2010)
            Exacerbations of chronic obstructive pulmonary disease (COPD) determine disease-associated morbidity, mortality, resource burden and healthcare costs. Acute exacerbation care requirements range from unscheduled primary care visits to emergency room, inpatient or intensive care, generating significant costs in COPD. Even after an exacerbation resolves, respiratory, physical, social and emotional impairment may persist for prolonged time. Frequent exacerbations, mainly in patients with severe COPD, accelerate disease progression and mortality. Thus, patients with frequent exacerbations have a more rapid decline in lung function, worse quality of life and decreased exercise performance. Management of COPD directed to reduce incidence and severity of exacerbations improves long-term health status and conserves health care resources and costs.
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              Air pollution and daily admissions for chronic obstructive pulmonary disease in 6 European cities: results from the APHEA project.

              We investigated the short-term effects of air pollution on hospital admissions for chronic obstructive pulmonary disease (COPD) in Europe. As part of a European project (Air Pollution and Health, a European Approach (APHEA)), we analysed data from the cities of Amsterdam, Barcelona, London, Milan, Paris and Rotterdam, using a standardized approach to data eligibility and statistical analysis. Relative risks for daily COPD admissions were obtained using Poisson regression, controlling for: seasonal and other cycles; influenza epidemics; day of the week; temperature; humidity and autocorrelation. Summary effects for each pollutant were estimated as the mean of each city's regression coefficients weighted by the inverse of the variance, allowing for additional between-cities variance, as necessary. For all ages, the relative risks (95% confidence limits (95% CL)) for a 50 microg x m(-3) increase in daily mean level of pollutant (lagged 1-3 days) were (95% CL): sulphur dioxide 1.02 (0.98, 1.06); black smoke 1.04 (1.01, 1.06); total suspended particulates 1.02 (1.00, 1.05), nitrogen dioxide 1.02 (1.00, 1.05) and ozone (8 h) 1.04 (1.02, 1.07). The results confirm that air pollution is associated with daily admissions for chronic obstructive pulmonary disease in European cities with widely varying climates. The results for particles and ozone are broadly consistent with those from North America, though the coefficients for particles are substantially smaller. Overall, the evidence points to a causal relationship but the mechanisms of action, exposure response relationships and pollutant interactions remain unclear.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of Chronic Obstructive Pulmonary Disease
                01 December 2020
                : 15
                : 3147-3158
                [1 ]Primary Care, Population Sciences and Medical Education, University of Southampton , Southampton, England, UK
                [2 ]Centre for Trials Research, Cardiff University , Cardiff, Wales, UK
                [3 ]Specialist Antimicrobial Chemotherapy Unit, Microbiology Cardiff, Public Health Wales , Cardiff, Wales, UK
                [4 ]School of Population Health and Environmental Sciences, King’s College London , London, England, UK
                [5 ]Department of Community Medicine, UIT the Arctic University of Norway , Tromsø, Norway
                [6 ]Nuffield Department of Primary Care Health Sciences, University of Oxford , Oxford, England, UK
                Author notes
                Correspondence: Nick A Francis Primary Care, Population Sciences and Medical Education, University of Southampton, Aldermoor Health Centre , SouthamptonSO16 5ST, UK Email
                © 2020 Francis et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (

                Page count
                Figures: 3, Tables: 6, References: 22, Pages: 12
                This study is a secondary analysis of data collected by a project funded by the NIHR Health Technology Assessment Program (project number 12/33/12). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. The work was undertaken with the support of: 1) The UK Clinical Research Collaboration (UKCRC) registered Clinical Trials Unit, the Centre for Trials Research, and funding from Health and Care Research Wales and Cancer Research UK, under the auspices of the UKCRC collaboration, is gratefully acknowledged, and; 2) The UK Clinical Research Collaboration (UKCRC) registered University of Oxford Primary Care and Vaccines Clinical Trials Collaborative.
                Original Research

                Respiratory medicine

                copd, exacerbation, infection, bacteria, sputum, primary care


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