Urinary Proteome Analysis by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry with Magnetic Beads for Identifying the Pathologic Presentation of Clinical Early IgA Nephropathy

IgA nephropathy is the most common type of chronic glomerulonephritis which leads eventually to end-stage renal disease (ESRD). The duration of clinical early stage IgA nephropathy to ESRD varies a lot. The pathologic presentation may have detrimental effect on outcome. But the renal biopsy is a high-risk invasive operation not able to be accepted by all patients. In this study, we tried to find biomarkers in urine as a non-invasive approach to diagnose different pathologic presentations of clinical early stage IgA nephropathy. A total of 56 patients with IgA nephropathy were included in this study, with 23 patients having severe pathologic presentation and the other 33 having mild ones. The control group consisted of 14 normal subjects. The urinary proteomic spectra from those three groups were generated by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with weak cationic exchange magnetic beads. The total experiment data was handled by the Zhejiang University ProteinChip Data Analysis System. We found that the urine protein/peptide spectra patterns could be established to distinguish severe IgA nephropathy from the mild IgA nephropathy group and the normal group. Several potential biomarkers were found and the diagnostic system could distinguish between severe IgA nephropathy from the mild IgA nephropathy with a sensitivity of 90.48% and specificity of 96.77%. We conclude that, using MALDI-TOF-MS with magnetic beads to detect urine proteomic patterns shows great potential in identifying early IgA nephropathy with different pathologic prognosis.