Galactose‐Deficient Immunoglobulin A1 Predicts Immunoglobulin A Nephropathy Recurrence After Kidney Transplantation: A Single‐Center Retrospective Study

ABSTRACT Background The recurrence of immunoglobulin A nephropathy (IgAN) after kidney transplantation (KT) is common and compromises long‐term graft survival; however, the early identification of patients at high risk of recurrence remains a clinical challenge. This study evaluated the roles of serum galactose‐deficient IgA1 (Gd‐IgA1), proliferation‐inducing ligand (APRIL), and B‐cell activating factor (BAFF) in predicting post‐transplant IgAN recurrence. Methods This retrospective case–control study included patients with primary IgAN who underwent KT at the First Affiliated Hospital, Sun Yat‐sen University, from September 2014 to June 2023. Patients were divided into two groups: post‐transplantation IgAN recurrence ( n = 19) and non‐recurrence ( n = 25). Serum levels of Gd‐IgA1, APRIL, and BAFF were measured pre‐transplantation and at 3, 6, 12, 24, and 36 months post‐transplantation. Results Recipients of kidneys from living donors had a significantly higher risk of IgAN recurrence compared with deceased‐donor recipients (odds ratio = 30.6, p = 0.001). Serum Gd‐IgA1 levels showed good discriminative ability for recurrence at 3 months (area under the curve: 0.85, 95% confidence interval: 0.72–0.99) and 6 months (area under the curve: 0.89, 95% confidence interval: 0.76–1.00) after transplantation. Elevated Gd‐IgA1 levels at 3 and 6 months were significantly associated with recurrence in univariate analyses, and remained the only independent predictor in multivariate Cox models. BAFF levels were significantly lower in the recurrence group at 12 months, while APRIL levels did not differ between the groups at any time point. Conclusions Serum Gd‐IgA1 levels could effectively predict IgAN recurrence risk in patients post‐KT.