Clinical and pathological factors associated with eGFR slope in IgA nephropathy: a single-center retrospective cohort...

IgA nephropathy (IgAN) has a heterogeneous clinical course. We retrospectively studied 180 patients with biopsy-proven IgAN and at least 3 years of clinical follow-up. Patient-specific eGFR slopes were estimated from available measurements at biopsy and the 6-, 12-, 18-, 24-, 30-, and 36-month follow-up points. We built a post hoc multivariable model guided by clinical relevance. Oxford T was treated as categorical, with T0 as reference. The median eGFR slope was -1.12 mL/min/1.73 m²/year, and 35 patients (19.4%) met the operational rapid-progression threshold of < -5 mL/min/1.73 m²/year. In the primary model, higher ln(UACR + 1) predicted a steeper decline (β= -0.612, 95%CI -1.073 to -0.150). T2 lesions predicted a 3.87 mL/min/1.73 m²/year faster loss than T0 (β= -3.870, 95%CI -7.087 to -0.654), whereas T1 did not differ from T0. The model R² was 0.159 (adjusted R²=0.130). UACR and T2 estimates remained negative under HC3 inference and after excluding influential observations, although T2 was less stable in some restricted analyses. Baseline albuminuria was the most consistent adverse marker of eGFR slope. T2 lesions were linked to faster decline as well, but this estimate derived from only 16 patients (8.9%) and lost statistical significance when analysis was restricted to ≥5 measurements, making the finding tentative and strictly hypothesis-generating.