Abstract: Objective: To investigate risk factors for progressive renal function decline in IgA nephropathy (IgAN) patients who had achieved proteinuria levels meeting the current guideline-recommended target (<0.5 g/d). Methods: This was a single-center retrospective cohort study. Baseline data and follow-up data were retrospectively collected from patients diagnosed with IgAN by renal biopsy at the First Affiliated Hospital of Zhengzhou University between August 1, 2016 and April 30, 2022. The eGFR slope and time-averaged proteinuria (TAP) were estimated for each patient. Patients were divided into a target achievement group and a non-achievement group based on whether TAP was <0.5 g/d. Among patients in the target achievement group, those with an eGFR slope of <-1 mL/(min·1.73m²)/year were classified as the rapid progression group, and the remainder as the slow progression group. Logistic regression was used to identify factors associated with rapid renal function progression despite achievement of proteinuria control. Results: A total of 1 232 IgAN patients were enrolled, with a median follow-up of 38 months, a median TAP of 0.63 g/d, a mean eGFR slope of -0.75 mL/(min·1.73m²)/year, and 140 patients reached the endpoint event. Renal survival in the non-achievement group was significantly lower than that in the target achievement group (Log-rank P<0.001). Among the 485 patients with TAP<0.5 g/d, 160 still exhibited rapid renal function progression. Logistic regression showed that induction-phase corticosteroid/immunosuppressant therapy was independently associated with a reduced risk of rapid renal function progression, while baseline eGFR was independently associated with an increased risk. Conclusion: Among IgAN patients with time-averaged proteinuria<0.5 g/d, induction-phase corticosteroid/immunosuppressant therapy was associated with delaying renal function progression, regardless of baseline eGFR levels.

Key words: IgA nephropathy, time-averaged proteinuria, eGFR slope, risk factors, prognostic analysis