Background: The International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification represents the gold standard for the histological evaluation of Systemic Lupus Erythematosus (SLE) nephritis. A repeat biopsy (RB) might be an important tool to provide information on long-term renal outcomes and optimal therapy. Aims of this study were to evaluate the use of the ISN/RPS classification and the role of RB in routine clinical practice.
Methods: A total number of 142 patients with SLE nephritis and with adequate reference and RB samples were included in this multicentre retrospective study. A meticulous histological examination was centrally performed on first and RB and compared with clinical variables and follow-up data.
Results: Morphological features of the ISN/RPS classification: at first and RB, significant differences were observed between segmental classes (III, IV-S) and Class IV-G in mesangial proliferation, wire loops and tuft necrosis. Clinical features and ISN/RPS classification: the correlation between serum creatinine, proteinuria, blood pressure levels and histological classes at first and RB demonstrated more severe renal disease in Class IV-G, both at first and RB. Agreement between ISN/RPS classification at first and RB: 40.8% of patients changed the histological class. Fifty per cent of Class II (mild mesangial form) were reclassified as Class IV-G at RB, whereas 18.9% of Class IV-G were reclassified as Class II. The transition among segmental (III/IV-S) and mesangial forms (II/IV-G) was extremely rare. The comparison between the clinical parameters at the final follow-up and the ISN/RPS classification confirmed that the trend of serum creatinine and proteinuria between the different classes was better described at the RB (higher in Class IV-G) than on the first biopsy.
Conclusions: The histopathological data suggest that morphological differences between segmental and global forms do exist, possibly due to different pathogenetic mechanisms. An RB strategy could provide additional information on long-term renal outcomes. A strategy of protocol biopsies could be useful in perspective future trials to better understand the therapeutic response and the natural history of this disease.
Keywords: SLE nephritis; repeat biopsy.