Rapidly progressive iga nephropathy: clinicopathological characteristics and outcomes assessed according to the revised definition of the KDIGO 2021 guideline

Abstract

Background: Rapidly progressive IgA nephropathy (RPIgAN) is a severe clinical phenotype of IgAN, associated with a poor outcome. The recently published KDIGO 2021 Guideline for the Management of Glomerular Diseases has proposed a new definition for RPIgAN, which is based simply on a ≥ 50% decline in eGFR ≤ 3 months. Methods: In 1,677 IgAN patients followed at a single centre in China, we evaluated the utility of this new definition to identify the highest risk IgAN patients who might be suitable for combination immunosuppressive therapy. Results: The proportion of a ≥ 50% decline in eGFR ≤ 3 months was 5.2%. The majority of these patients had reversible causes, only 2.3% (39/1,677) meeting the KDIGO 2021 criteria for RPIgAN. These patients had a significantly higher risk for ESKD than non-RPIgAN patients (log rank P < 0.001). RPIgAN was an independent risk factor for ESKD (hazard ratio [HR] 3.99; 95% confidence interval [CI] 2.25 - 7.09; P < 0.001). A minority of the RPIgAN patients (25.6%) had ≥ 50% crescents. There was no significant difference in the risk for ESKD between patients in the RPIgAN group with ≥ 50% crescents and ˂ 50% crescents (log rank P = 0.27). Patients with RPIgAN and ≥ 50% crescents had a higher risk for ESKD than patients with non-RPIgAN and ≥ 50% crescents (log rank P = 0.04). Conclusions: These data support the validity of the KDIGO 2021 definition but require independent validation in other non-Chinese cohorts.