A multiplexed microflow LC–MS/MS-PRM assay for serologic quantification of IgG N- and HPX O- glycoforms in liver fibrosis

Targeted quantification of glycoproteins has not reached its full potential because of limitations of the existing analytical workflows. In this study, we introduce a targeted microflow LC–MS/MS-PRM method for the quantification of multiple glycopeptides in unfractionated serum samples. The entire preparation of 16 samples in a batch is completed within 3 h, and the LC–MS quantification of all the glycoforms in a sample is completed in 15 min in triplicate, including online capture and desalting. We demonstrate applicability of the workflow on a multiplexed quantification of eight N-glycoforms of immunoglobulin G (IgG) together with two O-glycoforms of hemopexin (HPX). We applied the assay to a serologic study of fibrotic liver disease in patients of HCV etiology. The results document that specific IgG- and HPX-glycoforms detect efficiently fibrotic disease of different degree, and suggest that the LC–MS/MS-PRM assays may provide rapid and reproducible biomarker assay targeting simultaneously the N- and O-glycoforms of the peptides. We propose that such high throughput multiplexed methods may advance the clinical use of the LC–MS/MS assays.