#1039 Characteristics and outcome of IgA nephropathy in Switzerland – a single center perspective
Authors: Taing Danny Thieny , Vogt Bruno , Mani Laila-Yasmin 
Published: May 2024

Abstract

Background and Aims
IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide leading to end-stage kidney disease (ESKD) in roughly 40% of affected patients by ten years. Geographic differences in clinical course and response to treatment may partly result from different disease entities. The purpose of this retrospective cohort analysis was to study all cases of IgAN from a single tertiary center with respect to clinical and histological characteristics, treatment practices and outcome.

Method
This retrospective cohort analysis identified 158 cases of adult biopsy-proven IgAN by chart review diagnosed between 1980 and 2017. Detailed phenotypisation including clinical, paraclinical, histological, treatment and outcome parameters was performed. Remission status was defined as described previously (Reich 2007). Statistical analysis was performed using Excel and SPSS software and included standard descriptive methods and included standard descriptive methods and student's t-test on a significance level of 0.05.

Results
Subjects were majorly male and of Caucasian descent. Mean estimated glomerular filtration rate (eGFR) according to Chronic Kidney Disease Epidemiology Collaboration formula at diagnosis was 55.3 ml/min/1.73 m2, mean proteinuria was 3.2 g/d. 70.3% of patients were hypertensive at presentation. Clinical presentation varied according to age. Thus, younger patients (18-39 years) presented more frequently with macrohematuria, asymptomatic urine abnormalities and by trend acute kidney injury whereas nephrotic syndrome and extrarenal symptoms were recorded in similar proportions of patients (Fig. 1). 28.5% of initial biopsies showed moderate to severe tubular atrophy and interstitial fibrosis (IFTA), 38% included crescents, 1.9% &gt; 50% crescents. 86.1% of the patients were treated by renin-angiotensin-aldosterone-system inhibitors, 46.8% received immunosuppressive therapy including steroids in 46.2% and other immunosuppressive medications in 19.6% the most common being azathioprine (Fig. 2). There were 33.5% complete and 13.3% partial remissions. Progression to ESKD was noted in 42.1%. 51.4% of patients treated with immunosuppressive therapy experienced remission. Recurrence rate after transplantation was 18.4%. Patients treated by immunosuppressants had higher levels of baseline proteinuria (3.2 ± 2.3 vs. 1.6 ± 1.6 g/d, p &lt; 0.00001), lower baseline eGFR (50 ± 31 vs. 61 ± 30 ml/min/1.73 m2, p = 0.04), higher number of crescents (9.4 ± 15.0 vs 2.3 ± 8.5%, p = 0.001), higher IFTA scores (1.7 ± 0.8 vs. 1.3 ± 0.6, p = 0.007) and higher fluorescence intensity scores for C3 (2.0 ± 0.9 vs. 1.6 ± 0.9, p = 0.02) on initial biopsy as compared to patients treated conservatively. Patients progressing to ESKD presented with higher blood pressure (146 ± 26 vs. 135 ± 18 mmHg systolic, p = 0.005; 89 ± 14 vs. 82 ± 14 mmHg diastolic, p = 0.006), lower eGFR (41 ± 29 vs. 64 ± 28 ml/min/1.73 m2, p = 0.00001), higher levels of proteinuria (3.4 ± 2.0 vs. 1.8 ± 1.9 g/d, p = 0.0001), higher number of crescents (9 ± 17 vs. 4 ± 9%, p = 0.03) and higher IFTA scores (1.8 ± 0.8 vs. 1.3 ± 0.6, p = 0.00001) as compared to patients without ESKD at last follow up. Baseline blood pressure (134 ± 18 vs. 147 ± 26 mmHg systolic, p = 0.004; 82 ± 14 vs. 89 ± 15 mmHg diastolic, p = 0.01), eGFR (60 ± 29 vs. 41 ± 27 mmHg, p = 0.0007), proteinuria (2.3 ± 1.9 vs. 3.2 ± 2.3 g/d, p = 0.03) and severity of IFTA (1.4 ± 0.6 vs. 1.8 ± 0.9, p = 0.003) differed significantly between patients who experienced any remission vs. those who did not achieve remission respectively.

Conclusion
This analysis gives insight into the characteristics and treatment practices of a Swiss single center cohort of IgAN patients from 1980-2017.