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Identification of a uromodulin fragment for diagnosis of IgA nephropathy.

IgA nephropathy (IgAN) is one of the most common types of glomerulonephritis worldwide and is diagnosed only with a renal biopsy. The purpose of the present studies was to identify the potential biomarkers for the non-invasive diagnosis of IgAN. The combination of a magnetic bead separation system with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to analyze urinary peptides of IgAN patients, other glomerulopathy patients, and healthy controls. ClinProTools v.2.0 software was also applied to establish a diagnostic model for IgAN. Our results demonstrated that 11 features had optimal discriminatory performance (p <0.00001). Among these features, the peptide with m/z 1913.14 was identified as a fragment of uromodulin. Receiver operating characteristic (ROC) analysis for m/z 1913.14 showed that the area under the curve (AUC) was 0.998 for distinguishing IgAN versus healthy controls, and 0.815 for distinguishing IgAN versus other glomerulopathy. Analysis of urine peptides patterns by the magnetic bead separation system and MALDI-TOF-MS was a non-invasive diagnostic tool. We conclude that the urinary peptide with m/z 1913.14, which was identified as a uromodulin fragment, may be used as a biomarker for the non-invasive diagnosis of IgAN clinically.