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Objectives Lupus nephritis (LN) affects approximately one-third of patients with Systemic Lupus Erythematosus (SLE). LN represents a major cause of morbidity and mortality, as it can progress to irreversible kidney damage, culminating in end-stage renal disease requiring dialysis or kidney transplantation. Although renal biopsy is the gold standard for diagnosis, serological biomarkers may help identify patients at risk and guide clinical decisions. The objective of this study was to establish Diagnostic Odds Ratios (DOR) for the associations between selected biomarkers including autoantibodies and clinical variables, which measure LN including any LN and classes of LN based on kidney biopsy.Methods Study participants fulfilling the SLE EULAR/ACR 2019 classification were identified by a search in electronic health records and included between 1. August 2023 and 31. October 2024. Autoantibody profiles, including anti-dsDNA (using titers positive (20 IU), 50, IU and 200 IU as thresholds), ANA, ENA, anti-Histon, aPL, ANCA-related, RA-related, IMM-related, and SSc-related autoantibodies, were analyzed on the day of visit and inclusion. Medical reviews were performed to obtain relevant renal outcomes, including if participants ever had any kidney manifestation, biopsy-proven LN, histological classes (II + V and III + IV), and proteinuria. Diagnostic odds ratios (DORs) with 95% confidence intervals were calculated for each biomarker.Results 185 patients with SLE were included. 36% (n=66) had LN, defined by renal biopsy with class II or V LN (n=14), renal biopsy with class III+IV LN (n=42) or proteinuria > 0.5 g/24 hr (n=65) ( table 1).Among evaluated biomarkers, anti-dsDNA > or equal to 200 IU/ml was associated with renal involvement (biopsy-proven LN: DOR = 3.61 [1.1–11.3]; class III + IV LN: DOR = 3.24 [1.02–10.2]). SSc-related autoantibodies were also associated with LN class III + IV: DOR = 6.96 [1.2–41.9]. Other autoantibodies, including ANA, ENA, and aPL, did not show significant associations across renal outcomes.Abstract PO:02:050 Table 1DOR - diagnostic odds ratio. *: according to medical recordsConclusions High anti-dsDNA titers (> or equal to 200 IU/ml) were the most reliable serological marker for biopsy-proven and proliferative LN (histology class III or IV) in a population-based study. Exploratory findings suggest potential roles for SSc-related antibodies as a group.