Abstract : ABSTRACT Renal biopsy is highly informative about diagnosis and prognosis in ANCA associated renal vasculitis. A prognostic classification including 4 types (focal, ascending, mixed and sclerotic) of glomerular changes was developed and validated by an international working group of renal pathologists in 2010. Surprisingly, this classification does’nt take into account tubulo-interstitial changes, which can sometimes affect renal prognosis. Our objective is to evaluate the prognostic correlation between this classification and tubulointerstitial lesions during ANCA associated renal vasculitis in our patients. This is a retrospective study enrolling 33 patients followed for extracapillary necrotizing pauci-immune glomerulonephritis between January 2009 and December 2018. Glomerular damage was subdivided into 4 types according to Berden et al. classification (2010). Tubulo-interstitial changes were assessed by the presence or absence of tubular necrosis and the rate of interstitial fibrosis/tubular atrophy (IF/TA). Renal outcome was assessed by GFR at 3 months and at the last visit. We used SPSS software (version 20) to look for a significant link between glomerular and tubulointerstitial lesions, then to seek for their correlation with renal survival. Renal biopsies were categorized as focal: n=4, crescentic: n=4, sclerotic: n=14 and mixed: n=11. Interstitial fibrosis and tubular atrophy (IF/TA) were present in 27 patients (81%). The rate of IF/TA varied between 10 and 100%. The distribution of TA/IF was comparable in the different categories of Berden classification: focal: 52.5 ± 34%, crescentic: 66.6 ± 49.3%, mixed: 60.4 ± 21.1% and sclerotic 52.7 ± 27%. Renal survival without end stage renal disease (ESRD) at 3 months was 50% for the focal class, 25% for the crescentic class, 28% for the mixed and 18% for the sclerotic class. Only the sclerotic class was statistically predictive of a poor renal outcome compared to the other classes. These classes didn’t show any significant evolutionary difference between them: p = 0.15 between focal and crescentic classes, p = 0.36 between crescentic and mixed classes and p = 0.33 between focal mixed classes. Patients who normalized their renal function had a mean at 20 ± 14.1% of IF/TA, those who developed CKD had a mean at 56.25 ± 27.5% and those who progressed to ESRD had a mean IF/TA at 58, 21 ± 30.7%. In this work, IF/TA were significantly present even in focal or crescentic classes, altering then renal prognosis. Given these data, integration of the assessment of tubulo-interstitial chronic changes is necessary for a better prognostication of histological modifications during renal ANCA associated vasculitis. Keywords: ANCA associated vasculitis, Berden classification, Tubular atrophy, interstitial fibrosis, chronic kidney disease.

Keyword : ANCA associated vasculitis, Berden classification, Tubular atrophy, interstitial fibrosis, chronic kidney disease.