Efficacy of galactose-deficient IgA1 as a biomarker for predicting IgA nephropathy recurrence after kidney transplantation: a retrospective case-control study

Background Allogeneic kidney transplantation (KT) is an effective treatment for end-stage renal disease caused by progressing immunoglobulin A nephropathy (IgAN). However, the post-KT IgAN recurrence rate is high and can shorten long-term graft survival. Therefore, early prediction of IgAN recurrence risk is crucial for improving transplantation outcomes. We hypothesized that serum galactose-deficient IgA1 (Gd-IgA1), APRIL, B-cell activating factor (BAFF), and sCD89 levels could help predict IgAN recurrence post-KT. Thus, this study aimed to validate our hypothesis in Chinese patients with IgAN. Methods In this retrospective case-control study, we examined patients with primary IgAN who underwent KT at the First Affiliated Hospital, Sun Yat-sen University from September 2014 to December 2019. Patients were divided into post-transplantation IgAN recurrence (n = 12) and non-recurrence (n = 13) groups. Serum levels of Gd-IgA1, APRIL, BAFF, and sCD89 were measured at pre-transplantation and at 1–6, 6–12, 12–24, and > 24 months post-transplantation. Results The area under the curve for predicting IgAN recurrence at 1–6 months post-transplantation was 0.91 (95% confidence interval [CI], 0.78–1; cutoff, 4.2 µg/mL), 0.79 (95% CI, 0.58–1; cutoff, 933 pg/mL), and 0.8 (95% CI, 0.6–1; cutoff, 1791 pg/mL) for Gd-IgA1, BAFF, and APRIL, respectively. At 6–12 months post-transplantation, it was 0.82 (95% CI, 0.6–1; cutoff, 2.37 µg/mL) and 0.9 (95% CI, 0.74–1; cutoff, 992 pg/mL) for Gd-IgA1 and BAFF, respectively. Finally, at 12–24 months post-transplantation, it was 0.91 (95% CI, 0.76–1; cutoff, 3.83 µg/mL) for Gd-IgA1. Compared to patients with post-transplantation Gd-IgA1 levels < 4.2 µg/mL, patients with Gd-IgA1 levels ≥ 4.2 µg/mL at 1–6 months post-transplantation had a hazard ratio (HR) of 25.38 (95% CI, 2.5–257.88, p = 0.006) for IgAN recurrence. BAFF levels at 1–6 months post-transplantation were protective against IgAN recurrence (HR, 0.03; 95% CI, 0–0.48; p = 0.013). Conclusions Serum Gd-IgA1 levels could effectively predict IgAN recurrence risk in patients post-KT.