#5924 LATE DIAGNOSIS OF IGA NEPHROPATHY IN LOWER SAXONY (GERMANY) – CLINICAL AND HISTOPATHOLOGICAL DATA FROM 246 PATIENTS AT TIME OF INITIAL RENAL BIOPSY
Authors: Gienapp Amelie , Meyer Torsten , Eden Gabriele , Schmidt Bernhard , Schmidt-Ott Kai , Bräsen Jan Hinrich , Kielstein Jan T 
Published: June 2023

Abstract

Background and Aims
IgA Nephropathy (IgAN) is the most frequent glomerulonephritis and contributes significantly to the burden of dialysis dependence. If not detected in the context of screening health examinations e.g. for the military service, decline in renal function is usually unnoticed due to the lack of specific symptoms. After decades of limited pharmacological options, the advent of new therapies provides opportunities for early intervention. Age and renal function as well as proteinuria at the time of renal biopsy varies depending on healthcare systems but might influence the use of novel interventions. Publications from outside Germany report that eGFR at the time of first renal biopsy in IgAN varies between 73.8 and 94.9ml/min/1,73 m2. The age at the time of diagnosis is between 27 and 40 years. The aim of our study was to investigate renal function, degree of proteinuria as well as histological parameters at the time of first renal biopsy in patients with IgA nephropathy.

Method
This retrospective study evaluated data from two different tertiary care hospitals in Germany that that sent their renal biopsies to the Nephropathology Department at the Hannover Medical School from January 2012 – October 2022. Only initial biopsies from native kidneys were included. Histopathological parameters and clinical as well as laboratory parameters at the month of biopsy were obtained. eGFR was calculated according to the CKD-EPI formula.

Results
First time diagnosis of IgA nephropathy was made in 246 patients at a median age at of 45 (range 4–79) years, 76.8% were male. The median serum creatinine level was 1.44mg/dl, corresponding to a median eGFR of 43.0 (3.8–132) ml/min/1.73 m2. Surprisingly 49.5% of all patients were at CKD KDIGO GFR stage 3B or higher at the time of first biopsy (Figure 1). Median proteinuria was 1.84 (0.08 – 16.5) g/d in those patients where 24h urine collection was performed. 156 of 246 patients had microhematuria at the time of biopsy. Based on the Oxford classification &gt;50% had hypercellularity. Endocapillary hypercellularity was present in 24%. Segmental glomerulosclerosis was almost evenly distributed (S0:116 | S1:112). Tubular atrophy and interstitial fibrosis were visible in most biopsies in 0-25% of cortical area (T0:153 | T1:59 | T2:16). In 27.2% the C-score was analyzed, showing cellular and/or fibrocellular crescent in 26.8% of those patients. Thrombosis and necrosis were rather uncommon in initial biopsies of IgA Nephropathy.

Conclusion
The study shows that an IgA Nephropathy shows severe renal impairment at the time of diagnosis i.e. first renal biopsy, suggesting that patients are referred rather late for this diagnostic procedure. These regional data have to be validated in larger cohorts. If confirmed, measures for earlier screening and referral should be implemented to allow timely intervention thus lowering need for renal replacement therapy.