PO:15:215 | Evaluating the Prognostic Value of Modified NIH Indices and Total Renal Chronicity Score in Lupus Nephritis: a single center retrospective analysis

Alessandra Ida Celia¹, Andrea Ascione², Bruna Cerebelli², Martina Leopizzi², Cristiano Alessandri¹, Francesca Romana Spinelli¹, Fabrizio Conti¹ | ¹Reumaologia, Scienze Cliniche internistiche, anestesiologiche e cardiovascolari, Università La Sapienza di Roma, Italy; ²Anatomia patologica, Dipartimento di Scienze biotecnologiche medico-chirurgiche, Università La Sapienza di Roma, Italy

Kidney biopsy is essential for Lupus nephritis (LN) diagnosis and classification as proteinuria alone cannot distinguish between treatable inflammation and chronic kidney damage, nor can it differentiate between the International Society of Nephrology (ISN) LN classes. Although the modified NIH activity and chronicity indices (mAI and mCI), show potential in stratifying patients, they lack clinical validation and defined thresholds for identifying high-risk patients. This study aims to evaluate the prognostic value of the mAI, mCI, and other clinicopathological factors in a LN single cohort. Patients who underwent kidney biopsy between 2018 and 2024, were enrolled. Hystological lesions were quantified based on the revised 2018 ISN/RPS classification for LN and the modified NIH scoring system. Additionally, the Total Renal Chronicity Score (TRCS), a score for glomerular diseases, was measured. Renal endpoints included achievement of complete renal response (CRR) at 1 year (defined as proteinuria <0.5g/day, withdrawal of glucocorticoid therapy, estimated glomerular filtration rate (eGFR) >90% of baseline). A combined negative outcome (CO) at 1 and 2 years was also assessed, defined by the occurrence of end-stage kidney disease (ESKD), a 25% decrease from the baseline eGFR or an increase in proteinuria of more than 50% from baseline. 35 LN patients were included: 80% with proliferative, 9% with pure membranous, and 11% with mesangioroliferative LN . The average mAI and mCI indices were 5.46 ± 3.6 and 2.71 ± 1.4, respectively. CRR was achieved by 65.7% of patients at 1 year, 31.4% met CO at 1 year and 34.3% at 2 years. The mAI was not significantly associated with any of the selected outcomes and was unable to predict eGFR variation at any point in the disease course. At univariate analysis, mCI correlated with eGFR at 6 months (p = 0,04) and 1 year (p=0,02). There was also an association between mCI and no CRR at 1 year(p=0,001); however, this association didn’t persist at multivariate analysis. When categorized using TRCS thresholds, tubular atrophy emerged as the most promising prognostic individual variable at both univariate and multivariate testing. The TRCS showed similar performance to the mCI in prediction of CRR at 1 year and eGFR at 6 months (p=0,01) and 1 year (p < 0,01). Furthermore, there was a strong association between TRCS and eGFR value at the time of biopsy (p=0,046) and at 2 years (p = 0,02). This study confirms the limited prognostic value of mAI and mCI in LN, with mAI showing no predictive utility and mCI losing significance in multivariate analysis. In contrast, the TRCS, especially tubular atrophy, emerged as a strong and independent predictor of renal outcomes. These findings underscore the need to refine mNIH scoring systems to enhance prognostic accuracy and guide treatment decisions in LN.