@article {Vanoverschelde58, author = {Anna Vanoverschelde and Samer R. Khan and Virgil A.S.H. Dalm and Layal Chaker and Guy Brusselle and Bruno H. Stricker and Lies Lahousse}, title = {Association between serum IgG levels and time to first antibiotic prescription in COPD patients}, volume = {8}, number = {suppl 8}, elocation-id = {58}, year = {2022}, doi = {10.1183/23120541.LSC-2022.58}, publisher = {European Respiratory Society}, abstract = {Background:~Low serum immunoglobulin G (IgG) levels have been associated with more antibiotic treatments in Chronic Obstructive Pulmonary Disease (COPD) patients, increased incidence of COPD-related hospitalizations, and more severe pneumonia. However, it is not known which group of COPD patients are most at risk for respiratory tract infections (RTIs) requiring antibiotic treatment.Aim:~To examine the association between IgG level and time to antibiotic prescription in COPD patients stratified by smoking status.Methods:~COPD patients from the prospective, population-based Rotterdam study with baseline IgG measurements were included. After exclusion of current antibiotic users, Cox proportional-hazards regression models were performed to investigate the association of IgG levels with time to first antibiotic prescription and adjusted for age, sex, BMI, diabetes, C-reactive protein levels, current oral corticosteroid use and antibiotic use in the year before (yes/no).Results:~In total, 501 COPD patients were included (mean age 67 y, 47\% female). Half of these patients were former smokers (n=248), more than one third current smokers (n=175), and 16\% never smokers (n=78). Median (Q1-Q3) IgG level was 9.3 (7.9-11.0) g/L. Only among currently smoking COPD patients, a significantly increased risk for being treated with antibiotics was observed with lower (Q1; HR 1.98; 95\% CI 1.26-3.13), and higher IgG levels (Q4; HR 1.84; 95\% CI 1.10-3.10) compared to Q3.Conclusion:~Currently smoking COPD patients with lower and higher IgG levels are most at risk for RTIs. The effects of current smoking on the immune response against bacterial RTIs should be further investigated to better guide treatment.FootnotesCite this article as ERJ Open Research 2022; 8: Suppl. 8, 58.This article was presented at the 2022 ERS Lung Science Conference, in session {\textquotedblleft}Poster Session 2{\textquotedblright}.This is an ERS Lung Science Conference abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).}, URL = {https://openres.ersjournals.com/content/8/suppl_8/58}, eprint = {https://openres.ersjournals.com/content}, journal = {ERJ Open Research} }