{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,11]],"date-time":"2026-08-11T07:31:04Z","timestamp":1786433464611,"version":"build-2736575974"},"reference-count":35,"publisher":"Springer Science and Business Media LLC","issue":"1","license":[{"start":{"date-parts":[[2026,5,23]],"date-time":"2026-05-23T00:00:00Z","timestamp":1779494400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T00:00:00Z","timestamp":1784678400000},"content-version":"vor","delay-in-days":60,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["BMC Pulm Med"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder in which chronic bronchitis and emphysema coexist to varying degrees. Emphysema has distinct clinical and prognostic features. C-reactive protein (CRP), procalcitonin (PCT), white blood cell count (WBC), and neutrophil values are used for diagnosing community-acquired pneumonia (CAP). This study investigated whether these biomarkers differ in emphysematous patients with CAP.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Patients with COPD hospitalized with CAP between January 2016 and February 2023 were divided into emphysema and non-emphysema groups based on radiologic findings. Emphysema subtypes were classified, and quantitative Goddard scoring was performed. Admission demographic, clinical and laboratory data, hospital stay length and clinical outcomes (discharge, intensive care unit [ICU] transfer, in-hospital mortality) were compared between groups. CRP and PCT levels were dichotomized as low and high using predefined thresholds (CRP\u2009\u2264\u2009200 vs. &gt;200\u00a0mg\/L; PCT\u2009&lt;\u20090.10 vs. \u22650.10\u00a0\u00b5g\/L). The independent effect of emphysema on low CRP and PCT levels was assessed using multivariable binary logistic regression analysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Of the 135 patients included, 71 (53%) had emphysema. Median CRP and PCT levels were significantly lower in the emphysema group than in the non-emphysema group (CRP: 116, interquartile range [IQR] 56\u2013187 vs. 254 (IQR 213-310\u00a0mg\/L);\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.001; PCT: 0.132 [ IQR 0.079\u20130.536] vs. 0.356 [IQR 0.171\u20131.660] \u00b5g\/L;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.007, respectively). Median WBC and neutrophil counts were also lower (\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.036;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.035, respectively). In multivariable analysis, emphysema (odds ratio [OR] 54.274; 95% Confidence Interval [CI] 14.545\u2013202.526;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.001), higher glomerular filtration rate (OR 1.021; 95% CI 1.002\u20131.040;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.026), and prior antibiotic use (OR 4.278; 95% CI 1.199\u201315.264;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.025) were independently associated with low CRP. For low PCT, emphysema remained the only significant predictor (OR 3.694; 95% CI 1.145\u201311.921;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.029). Length of stay was longer in emphysema (9 vs.7 days;\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20090.010), with no differences in ICU transfer or mortality.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>In patients with emphysema, inflammatory biomarkers at CAP diagnosis were lower compared with those without emphysema. These findings suggest a potential difference in biomarker response; however, the retrospective design limits causality. Further prospective studies are needed to confirm these results and clarify their clinical relevance.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial registration<\/jats:title>\n                    <jats:p>Not applicable. This study is a retrospective observational analysis and was not registered as a clinical trial.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12890-026-04364-2","type":"journal-article","created":{"date-parts":[[2026,5,23]],"date-time":"2026-05-23T04:44:53Z","timestamp":1779511493000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Impact of emphysema on biomarkers in hospitalized COPD patients with community-acquired pneumonia: a retrospective study"],"prefix":"10.1186","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-6134-1821","authenticated-orcid":false,"given":"Rabia","family":"Yurt","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9694-7909","authenticated-orcid":false,"given":"Meltem","family":"Agca","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6484-0039","authenticated-orcid":false,"given":"Ayla","family":"Turkar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5046-1943","authenticated-orcid":false,"given":"Eylem","family":"Tuncay","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1163-125X","authenticated-orcid":false,"given":"Sinem","family":"Gungor","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2380-5410","authenticated-orcid":false,"given":"Nazli Huma","family":"Teke","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9129-5497","authenticated-orcid":false,"given":"Baran","family":"Gundogus","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2443-2639","authenticated-orcid":false,"given":"Sibel","family":"Arinc","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3448-3675","authenticated-orcid":false,"given":"Ipek","family":"Ozmen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,5,23]]},"reference":[{"key":"4364_CR1","unstructured":"World Health Organization. Chronic obstructive pulmonary disease (COPD). Eastern Mediterranean Regional Office, WHO. Available from:https:\/\/www.emro.who.int\/health-topics\/chronic-obstructive-pulmonary-disease-copd\/. Accessed 24 Dec 2025."},{"key":"4364_CR2","unstructured":"Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2024 report. 2024. Available from: https:\/\/goldcopd.org\/2024-gold-report\/.\u00a0 Accessed 22 May 2026."},{"issue":"1","key":"4364_CR3","doi-asserted-by":"publisher","first-page":"182","DOI":"10.1164\/arrd.1985.132.1.182","volume":"132","author":"GL Snider","year":"1985","unstructured":"Snider GL, Kleinerman J, Thurlbeck WM, Bengali ZH. The definition of emphysema: report of a National Heart, Lung and Blood Institute, Division of Lung Diseases Workshop. Am Rev Respir Dis. 1985;132(1):182\u20135. https:\/\/doi.org\/10.1164\/arrd.1985.132.1.182.","journal-title":"Am Rev Respir Dis"},{"issue":"17","key":"4364_CR4","doi-asserted-by":"publisher","first-page":"1619","DOI":"10.1056\/NEJMra1312885","volume":"371","author":"DM Musher","year":"2014","unstructured":"Musher DM, Thorner AR. Community-acquired pneumonia. N Engl J Med. 2014;371(17):1619\u201328. https:\/\/doi.org\/10.1056\/NEJMra1312885.","journal-title":"N Engl J Med"},{"key":"4364_CR5","unstructured":"World Health Organization. WHO reveals leading causes of death and disability worldwide: 2000\u20132019. December 2020. Available from:https:\/\/www.who.int\/news\/item\/09-12-2020-who-reveals-leading-causes-of-death-and-disability-worldwide-2000-2019. Accessed 24 Dec 2025."},{"issue":"11","key":"4364_CR6","doi-asserted-by":"publisher","first-page":"1806","DOI":"10.1093\/cid\/cix647","volume":"65","author":"JA Ramirez","year":"2017","unstructured":"Ramirez JA, Wiemken TL, Peyrani P, Arnold FW, Kelley R, Mattingly WA, et al. Adults hospitalized with pneumonia in the United States: incidence, epidemiology, and mortality. Clin Infect Dis. 2017;65(11):1806\u201312. https:\/\/doi.org\/10.1093\/cid\/cix647.","journal-title":"Clin Infect Dis"},{"issue":"2","key":"4364_CR7","doi-asserted-by":"publisher","first-page":"173","DOI":"10.1097\/QCO.0000000000000639","volume":"33","author":"R Cavallazzi","year":"2020","unstructured":"Cavallazzi R, Ramirez J. Community-acquired pneumonia in chronic obstructive pulmonary disease. Curr Opin Infect Dis. 2020;33(2):173\u201381. https:\/\/doi.org\/10.1097\/QCO.0000000000000639.","journal-title":"Curr Opin Infect Dis"},{"key":"4364_CR8","doi-asserted-by":"publisher","first-page":"587","DOI":"10.2147\/COPD.S32765","volume":"7","author":"R Jen","year":"2012","unstructured":"Jen R, Rennard SI, Sin DD. Effects of inhaled corticosteroids on airway inflammation in chronic obstructive pulmonary disease: a systematic review and meta-analysis. Int J Chron Obstruct Pulmon Dis. 2012;7:587\u201395. https:\/\/doi.org\/10.2147\/COPD.S32765.","journal-title":"Int J Chron Obstruct Pulmon Dis"},{"key":"4364_CR9","doi-asserted-by":"publisher","first-page":"219","DOI":"10.1183\/09031936.00150208","volume":"34","author":"GG Brusselle","year":"2009","unstructured":"Brusselle GG, Demoor T, Bracke KR, Brandsma CA, Timens W. Lymphoid follicles in (very) severe COPD: beneficial or harmful? Eur Respir J. 2009;34:219\u201330. https:\/\/doi.org\/10.1183\/09031936.00150208.","journal-title":"Eur Respir J"},{"issue":"4","key":"4364_CR10","doi-asserted-by":"publisher","first-page":"1009","DOI":"10.1378\/chest.12-1684","volume":"143","author":"E Crisafulli","year":"2013","unstructured":"Crisafulli E, Menendez R, Huerta A, et al. Systemic inflammatory pattern of patients with community-acquired pneumonia with and without COPD. Chest. 2013;143(4):1009\u201317. https:\/\/doi.org\/10.1378\/chest.12-1684.","journal-title":"Chest"},{"issue":"2","key":"4364_CR11","doi-asserted-by":"publisher","first-page":"285","DOI":"10.1183\/09031936.00118909","volume":"36","author":"P Gutierrez","year":"2010","unstructured":"Gutierrez P, Closa D, Piner R, Bulbena O, Menendez R, Torres A. Macrophage activation in exacerbated COPD with and without community-acquired pneumonia. Eur Respir J. 2010;36(2):285\u201391. https:\/\/doi.org\/10.1183\/09031936.00118909.","journal-title":"Eur Respir J"},{"key":"4364_CR12","doi-asserted-by":"publisher","first-page":"1046","DOI":"10.1111\/resp.12597","volume":"20","author":"HL Jiang","year":"2015","unstructured":"Jiang HL, Chen HX, Liu W, Fan T, Liu GJ, Mao B, et al. Is COPD associated with increased mortality and morbidity in hospitalized pneumonia? A systematic review and meta-analysis. Respirology. 2015;20:1046\u201354. https:\/\/doi.org\/10.1111\/resp.12597.","journal-title":"Respirology"},{"issue":"2","key":"4364_CR13","doi-asserted-by":"publisher","first-page":"203","DOI":"10.1586\/ers.12.6","volume":"6","author":"S Kr\u00fcger","year":"2012","unstructured":"Kr\u00fcger S, Welte T. Biomarkers in community-acquired pneumonia. Expert Rev Respir Med. 2012;6(2):203\u201314. https:\/\/doi.org\/10.1586\/ers.12.6.","journal-title":"Expert Rev Respir Med"},{"issue":"6","key":"4364_CR14","doi-asserted-by":"publisher","first-page":"1410","DOI":"10.1378\/chest.10-1747","volume":"139","author":"M Bafadhel","year":"2011","unstructured":"Bafadhel M, Clark TW, Reid C, et al. Procalcitonin and C-reactive protein in hospitalized adult patients with community-acquired pneumonia or exacerbation of asthma or COPD. Chest. 2011;139(6):1410\u20138. https:\/\/doi.org\/10.1378\/chest.10-1747.","journal-title":"Chest"},{"key":"4364_CR15","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1177\/1479972318769762","volume":"16","author":"E Titova","year":"2019","unstructured":"Titova E, Christensen A, Henriksen AH, et al. Comparison of procalcitonin, C-reactive protein, white blood cell count and clinical status in diagnosing pneumonia in patients hospitalized with acute exacerbations of COPD: a prospective observational study. Chron Respir Dis. 2019;16:1\u20139. https:\/\/doi.org\/10.1177\/1479972318769762.","journal-title":"Chron Respir Dis"},{"issue":"4","key":"4364_CR16","doi-asserted-by":"publisher","first-page":"586","DOI":"10.1183\/09031936.05.00021005","volume":"26","author":"V Cottin","year":"2005","unstructured":"Cottin V, Nunes H, Brillet PY, et al. Combined pulmonary fibrosis and emphysema: a distinct under recognised entity. Eur Respir J. 2005;26(4):586\u201393. https:\/\/doi.org\/10.1183\/09031936.05.00021005.","journal-title":"Eur Respir J"},{"issue":"4","key":"4364_CR17","doi-asserted-by":"publisher","first-page":"379","DOI":"10.1016\/s0009-9260(82)80301-2","volume":"33","author":"PR Goddard","year":"1982","unstructured":"Goddard PR, Nicholson EM, Laszlo G, Watt I. Computed tomography in pulmonary emphysema. Clin Radiol. 1982;33(4):379\u201387. https:\/\/doi.org\/10.1016\/s0009-9260(82)80301-2.","journal-title":"Clin Radiol"},{"issue":"4","key":"4364_CR18","doi-asserted-by":"publisher","first-page":"243","DOI":"10.1056\/NEJM199701233360402","volume":"336","author":"MJ Fine","year":"1997","unstructured":"Fine MJ, Auble TE, Yealy DM, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997;336(4):243\u201350. https:\/\/doi.org\/10.1056\/NEJM199701233360402.","journal-title":"N Engl J Med"},{"issue":"5","key":"4364_CR19","doi-asserted-by":"publisher","first-page":"377","DOI":"10.1136\/thorax.58.5.377","volume":"58","author":"WS Lim","year":"2003","unstructured":"Lim WS, van der Eerden MM, Laing R. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58(5):377\u201382. https:\/\/doi.org\/10.1136\/thorax.58.5.377.","journal-title":"Thorax"},{"key":"4364_CR20","doi-asserted-by":"publisher","DOI":"10.1155\/2016\/2198745","volume":"2016","author":"A Ruiz-Gonz\u00e1lez","year":"2016","unstructured":"Ruiz-Gonz\u00e1lez A, Utrillo L, Bielsa S, Falguera M, Porcel JM. The diagnostic value of serum C-Reactive Protein for identifying pneumonia in hospitalized patients with acute respiratory symptoms. J Biomarkers. 2016;2016:2198745. https:\/\/doi.org\/10.1155\/2016\/2198745.","journal-title":"J Biomarkers"},{"issue":"1","key":"4364_CR21","doi-asserted-by":"publisher","DOI":"10.1186\/s12873-017-0138-1","volume":"17","author":"DT Huang","year":"2017","unstructured":"Huang DT, Angus DC, Chang CCH, Doi Y, Fine MJ, Kellum JA, et al. Design and rationale of the Procalcitonin Antibiotic Consensus Trial (ProACT), a multicenter randomized trial of procalcitonin antibiotic guidance in lower respiratory tract infection. BMC Emerg Med. 2017;17(1):25. https:\/\/doi.org\/10.1186\/s12873-017-0138-1.","journal-title":"BMC Emerg Med"},{"issue":"2 Suppl 1","key":"4364_CR22","first-page":"S1","volume":"39","author":"National Kidney Foundation","year":"2002","unstructured":"National Kidney Foundation. K\/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis. 2002;39(2 Suppl 1):S1-266.","journal-title":"Am J Kidney Dis"},{"issue":"7","key":"4364_CR23","doi-asserted-by":"publisher","first-page":"826","DOI":"10.1111\/crj.13370","volume":"15","author":"H Seo","year":"2021","unstructured":"Seo H, Cha SI, Shin KM, Lim JK, Lee WK, Park JE, et al. Clinical relevance of emphysema in patients hospitalized with community-acquired pneumonia: clinical features and prognosis. Clin Respir J. 2021;15(7):826\u201334. https:\/\/doi.org\/10.1111\/crj.13370.","journal-title":"Clin Respir J"},{"issue":"1","key":"4364_CR24","doi-asserted-by":"publisher","first-page":"C73","DOI":"10.1152\/ajpcell.00110.2016","volume":"314","author":"N Vij","year":"2018","unstructured":"Vij N, Chandramani-Shivalingappa P, Van Westphal C, Hole R, Bodas M. Cigarette smoke-induced autophagy impairment accelerates lung aging, COPD-emphysema exacerbations and pathogenesis. Am J Physiol Cell Physiol. 2018;314(1):C73-87. https:\/\/doi.org\/10.1152\/ajpcell.00110.2016.","journal-title":"Am J Physiol Cell Physiol"},{"issue":"3","key":"4364_CR25","doi-asserted-by":"publisher","first-page":"317","DOI":"10.2169\/internalmedicine.52.8830","volume":"52","author":"T Ishiguro","year":"2013","unstructured":"Ishiguro T, Takayanagi N, Yamaguchi S, Yamakawa H, Nakamoto K, Takaku Y, et al. Etiology and factors contributing to the severity and mortality of community-acquired pneumonia. InternMed. 2013;52(3):317\u201324. https:\/\/doi.org\/10.2169\/internalmedicine.52.8830.","journal-title":"InternMed"},{"key":"4364_CR26","doi-asserted-by":"publisher","first-page":"69","DOI":"10.1016\/j.ejim.2017.06.008","volume":"43","author":"J De Miguel-D\u00edez","year":"2017","unstructured":"De Miguel-D\u00edez J, L\u00f3pez-de-Andr\u00e9s A, Hern\u00e1ndez-Barrera V, et al. Impact of COPD on outcomes in hospitalized patients with community-acquired pneumonia: analysis of the Spanish national hospital discharge database (2004\u20132013). Eur J InternMed. 2017;43:69\u201376. https:\/\/doi.org\/10.1016\/j.ejim.2017.06.008.","journal-title":"Eur J InternMed"},{"issue":"1","key":"4364_CR27","doi-asserted-by":"publisher","first-page":"496","DOI":"10.1186\/s12890-024-03305-1","volume":"24","author":"F Zheng","year":"2024","unstructured":"Zheng F, WangX. Effect of pneumonia on the outcomes of acute exacerbation of chronic obstructive pulmonary disease: a systematic review and meta-analysis. BMC PulmonaryMedicine. 2024;24(1):496. https:\/\/doi.org\/10.1186\/s12890-024-03305-1.","journal-title":"BMC PulmonaryMedicine"},{"key":"4364_CR28","doi-asserted-by":"publisher","first-page":"187","DOI":"10.4046\/trd.2018.0030","volume":"81","author":"MI Restrepo","year":"2018","unstructured":"Restrepo MI, Sibila O, Anzueto A. Pneumonia in patients with chronic obstructive pulmonary disease. Tuberc Respir Dis. 2018;81:187\u201397. https:\/\/doi.org\/10.4046\/trd.2018.0030.","journal-title":"Tuberc Respir Dis"},{"issue":"2","key":"4364_CR29","doi-asserted-by":"publisher","first-page":"91","DOI":"10.4046\/trd.2016.79.2.91","volume":"79","author":"Y Hong","year":"2016","unstructured":"Hong Y, Lee JS, Yoo KH, Lee JH, Kim WJ, Lim SY, et al. Implications of emphysema and lung function for the development of pneumonia in patients with chronic obstructive pulmonary disease. TubercRespirDis (Seoul). 2016;79(2):91\u20137. https:\/\/doi.org\/10.4046\/trd.2016.79.2.91.","journal-title":"TubercRespirDis (Seoul)"},{"issue":"2","key":"4364_CR30","doi-asserted-by":"publisher","first-page":"105","DOI":"10.4103\/1817-1737.151441","volume":"10","author":"JS Eom","year":"2015","unstructured":"Eom JS, Song WJ, Yoo H, Jeong BH, Lee HY, Koh WJ, et al. Chronic obstructive pulmonary disease severity is associated with severe pneumonia. Ann Thorac Med. 2015;10(2):105\u201311. https:\/\/doi.org\/10.4103\/1817-1737.151441.","journal-title":"Ann Thorac Med"},{"issue":"6","key":"4364_CR31","doi-asserted-by":"publisher","first-page":"964","DOI":"10.1183\/09031936.04.00064004","volume":"24","author":"T Betsuyaku","year":"2004","unstructured":"Betsuyaku T, Kuroki Y, Nagai K, Nasuhara Y, Nishimura M. Effects of ageing and smoking on SP-A and SP-D levels in bronchoalveolar lavage fluid. Eur Respir J. 2004;24(6):964\u201370. https:\/\/doi.org\/10.1183\/09031936.04.00064004.","journal-title":"Eur Respir J"},{"issue":"1","key":"4364_CR32","doi-asserted-by":"publisher","DOI":"10.1186\/s12931-018-0734-y","volume":"19","author":"K Ostridge","year":"2018","unstructured":"Ostridge K, Williams NP, Kim V, Harden S, Bourne S, Clarke SC, et al. Relationship of CT-quantified emphysema, small airways disease and bronchial wall dimensions with physiological, inflammatory and infective measures in COPD. Respir Res. 2018;19(1):31. https:\/\/doi.org\/10.1186\/s12931-018-0734-y.","journal-title":"Respir Res"},{"issue":"2","key":"4364_CR33","doi-asserted-by":"publisher","first-page":"275","DOI":"10.1016\/j.rmed.2009.09.016","volume":"104","author":"AI Papaioannou","year":"2010","unstructured":"Papaioannou AI, Mazioti A, Kiropoulos T, Tsilioni I, Koutsokera A, Tanou K, et al. Systemic and airway inflammation and the presence of emphysema in patients with COPD. Respir Med. 2010;104(2):275\u201382. https:\/\/doi.org\/10.1016\/j.rmed.2009.09.016.","journal-title":"Respir Med"},{"issue":"2","key":"4364_CR34","doi-asserted-by":"publisher","first-page":"206","DOI":"10.1086\/421997","volume":"39","author":"L Simon","year":"2004","unstructured":"Simon L, Gauvin F, Amre DK, Saint-Louis P, Lacroix J. Serum procalcitonin and C-reactive protein levels as markers of bacterial infection: a systematic review and meta-analysis. Clin Infect Dis. 2004;39(2):206\u201317. https:\/\/doi.org\/10.1086\/421997.","journal-title":"Clin Infect Dis"},{"issue":"7","key":"4364_CR35","doi-asserted-by":"publisher","first-page":"e45","DOI":"10.1164\/rccm.201908-1581ST","volume":"200","author":"JP Metlay","year":"2019","unstructured":"Metlay JP, Waterer GW, Long AC, Anzueto A, Brozek J, Crothers K, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45-67. https:\/\/doi.org\/10.1164\/rccm.201908-1581ST.","journal-title":"Am J Respir Crit Care Med"}],"container-title":["BMC Pulmonary Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/link.springer.com\/article\/10.1186\/s12890-026-04364-2","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1186\/s12890-026-04364-2.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1186\/s12890-026-04364-2.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,11]],"date-time":"2026-08-11T07:04:26Z","timestamp":1786431866000},"score":1,"resource":{"primary":{"URL":"https:\/\/link.springer.com\/10.1186\/s12890-026-04364-2"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,23]]},"references-count":35,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,12]]}},"alternative-id":["4364"],"URL":"https:\/\/doi.org\/10.1186\/s12890-026-04364-2","relation":{},"ISSN":["1471-2466"],"issn-type":[{"value":"1471-2466","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,23]]},"assertion":[{"value":"27 December 2025","order":1,"name":"received","label":"Received","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"18 May 2026","order":2,"name":"accepted","label":"Accepted","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"23 May 2026","order":3,"name":"first_online","label":"First Online","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"12 August 2026","order":6,"name":"change_date","label":"Change Date","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"Update","order":7,"name":"change_type","label":"Change Type","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"The numbers were updated as normal text, not as reference citations: Emphysema severity was categorized as mild (1\u20136), moderate (7\u201312), moderate-to-severe (13\u201318), and severe (19\u201324).","order":8,"name":"change_details","label":"Change Details","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"The study was conducted in accordance with the Declaration of Helsinki and was approved by the Sureyyapasa Chest Diseases and Thoracic Surgery Training and Research Hospital Non-Interventional Clinical Research Ethics Committee (Approval date: 16 March 2023; Approval No: 116.2017.R-286). Due to the retrospective nature of the study, the requirement for informed consent was waived. Patient data were fully anonymized prior to analysis, and access to the dataset was restricted to authorized investigators only.","order":1,"name":"Ethics","label":"Ethics approval and consent to participate","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"Not applicable.","order":2,"name":"Ethics","label":"Consent for publication","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"The authors declare no competing interests.","order":3,"name":"Ethics","label":"Competing interests","group":{"name":"EthicsHeading","label":"Declarations"}}],"article-number":"324"}}