A Novel Biomarker for Post-Transplant Recurrent IgA Nephropathy.

Background. The serum levels of galactose-deficient immunoglobulin (Ig)A1 (Gd-IgA1)represent the most promising candidate biomarker for IgA nephropathy (IgAN). The aimof this study was to evaluate the serum levels of Gd-IgA1 as a novel noninvasive biomarkerfor post-transplant IgAN recurrence.Methods. Serum Gd-IgA1 levels of 18 patients with recurrent IgAN were compared withcontrol renal transplant recipients (n ¼ 23) with non-recurrent IgAN and control nontransplantIgAN patients (n ¼ 44) and healthy relatives (n ¼ 11). Serum Gd-IgA1 levelsof patients were measured with the use of KM55 enzyme-linked immunosorbent assay(ELISA). The effects of serum Gd-IgA1 concentrations on IgAN recurrence, posttransplantevents, and graft survival were evaluated.Results. All recurrent IgAN patients presented with renal dysfunction (mean serumcreatinine, 1.62 0.39 mg/dL) and detectable proteinuria at the time of diagnosis. SerumGd-IgA1 levels of recurrent IgAN patients (8735 10854 ng/mL [log10: 3.71 0.45]) weresignificantly higher than those of non-recurrent IgAN patients (4790 6089 ng/mL [log10:3.31 0.64]) (P ¼ .027). Serum Gd-IgA1 levels of non-transplant IgAN patients weresignificantly higher (8791 8700 ng/mL [log10: 3.79 0.36]) than those of nonrecurrentIgAN patients (4790 6089 ng/mL [log10: 3.31 0.64]) and healthy relatives(2615 1611 ng/mL [log10: 3.34 0.27]) (P < .001 and P ¼ .021, respectively).Receiver-operating characteristic curve analysis revealed that the area under the curvefor recurrence of IgAN was 0.69 (0.53e0.85) for serum Gd-IgA1 (P ¼ .038). Biopsyconfirmedallograft rejection rates were similar in the recurrent IgAN group [3 (17%)]compared with the non-recurrent IgAN [6 (26%)] group (P ¼ .47). Graft failure ratewas not also significantly different in the recurrent IgAN group [4 (22.2%)] comparedwith the non-recurrent IgAN group [2 (8.7%)] (P ¼ .224).Conclusions. This novel lectin-independent Gd-IgA1 ELISA that can detect serum Gd-IgA1 in patients with recurrent IgAN can be used as a biomarker for diagnosis and activityassessment of post-transplant recurrent IgAN