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Investigating the role of pentraxin 3 as a biomarker for bacterial infection in subjects with COPD

Authors Thulborn SJ, Dilpazir M, Haldar K, Mistry V, Brightling CE, Barer MR, Bafadhel M

Received 30 September 2016

Accepted for publication 20 December 2016

Published 18 April 2017 Volume 2017:12 Pages 1199—1205

DOI https://doi.org/10.2147/COPD.S123528

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Professor Hsiao-Chi Chuang

Peer reviewer comments 2

Editor who approved publication: Dr Richard Russell

Samantha J Thulborn,1 Madiha Dilpazir,2 Koirobi Haldar,3 Vijay Mistry,3 Christopher E Brightling,3 Michael R Barer,3 Mona Bafadhel1

1Respiratory Medicine Unit, Nuffield Department of Medicine, University of Oxford, 2Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, 3Department of Immunity, Infection & Inflammation, University of Leicester, Leicester, UK

Background: Pentraxin 3 (PTX3) is an acute phase protein, involved in antibacterial resistance. Recent studies have shown PTX3 levels to be elevated in the presence of a bacterial infection and in a murine sepsis model.
Objective: We aim to investigate if sputum PTX3 can be used as a biomarker for bacterial infection in subjects with COPD.
Materials and methods: Sputum samples from 142 COPD patients (102 men) with a mean (range) age of 69 years (45–85) and mean (SD) post-bronchodilator percentage predicted forced expiratory volume in 1 second (FEV1) of 50% (19) were analyzed for PTX3, using a commercial assay at stable state and during an exacerbation. Association with bacteria, from culture, quantitative real-time polymerase chain reaction (qPCR) and colony-forming units (CFU) was investigated.
Results: The geometric mean (95% CI) PTX3 level at stable state was 50.5 ng/mL (41.4–61.7). PTX3 levels correlated with absolute neutrophil count in sputum (r=0.37; P<0.01), but not FEV1 or health status. There was a weak correlation between PTX3 and bacterial load (CFU: r=0.29, P<0.01; 16S qPCR: r=0.18, P=0.05). PTX3 was a poor predictor of bacterial colonization (defined as >105 CFU/mL at stable state) with a receiver-operating characteristic (ROC) area under the curve (AUC) of 0.59 and 95% confidence interval (CI) 0.43–0.76 (P=0.21). During an exacerbation, there was a modest increase in PTX3 (fold difference 0.15, 95% of difference 0.02–0.29; P=0.02), and PTX3 fared better at identifying a bacteria-associated exacerbation (ROC AUC 0.65, 95% CI 0.52–0.78, P=0.03).
Conclusion: PTX3 is associated with bacterial infection in patients with COPD, but its utility as a biomarker for identifying a bacteria-associated exacerbation warrants further studies.

Keywords: TNF-inducible gene 14 protein, infection, sputum

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