Abstract: Objective To investigate the potential of the absolute quantifaction of plasma IgG N-glycopeptides for the early diagnosis of chronic obstructive pulmonary disease (COPD). Methods Research objects were randomly selected from the healthy control (HC) group, the early COPD (ECOPD) group and the stable COPD(COPD) group from previous research cohort(20 cases for each group), and targeted differential glycopeptides were selected based on the previously obtained relative quantitative data of plasma IgG N-glycopeptides. Absolute concentration of glycopeptide was measured with internal standard method. The linear relationship between the absolute concentra- tion of the targeted glycopeptides and the ratio of forced expiratory volume in one second to forced vital capacity (FEV1/FVC) was analyzed. The receiver operating characteristic (ROC) curves were generated to compare the diagnostic efficacy of individual glycopeptides indicators, age, smoking index and their combination. Results The relative quantification showed that the plasma level of IgG2 G2FS glycopeptides was significantly higher in the HC group than that in the ECOPD and COPD groups (P＜0.05). The absolute quantification further clarified a successive decrease in its concentration across the HC, ECOPD, and COPD groups, with a particular difference between the HC and COPD groups (P＜0.001). ROC analysis indicated that the diagnostic efficacy of the plasma IgG2 G2FS concentration for ECOPD (area under curve,AUC=0.765) was superior to that of age (AUC=0.624) or smoking index (AUC=0.602). However, the combined model incorporating IgG2 G2FS, age, and smoking index (AUC=0.780) showed comparable performance to IgG2 G2FS alone. Conclusions The absolute concentration of plasma IgG2 G2FS exhibits competitive diagnostic value for early COPD, suggesting plasma IgG2 G2FS is a potential biomarker for early digestion of COPD.

Key words: chronic obstructive pulmonary disease, early diagnosis, N-glycosylation, immunoglobulin, absolute quantification