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Background:Treatment of systemic lupus erythematosus (SLE) is tailored according to the intensity of SLE disease activity and aims to achieve remission. Current definitions of remission and disease activity categories are mostly based on the SLE Disease Activity Index (SLEDAI), which has important limitations. The SLE Disease Activity Score (SLE-DAS) is a validated continuous disease activity score with higher accuracy in measuring SLE activity and higher sensitivity-to-change as compared to SLEDAI1. SLE-DAS is user-friendly with its online calculator.Objectives:To derive and validate the SLE-DAS cut-off values for defining SLE disease activity categories and SLE clinical remission state.Methods:Derivation study was conducted at the Padova Lupus Clinic. Validation was performed prospectively in patients from the Cochin Lupus Clinic and by post-hoc analysis of BLISS-76 (NCT00410384) trial. Gold-standard for clinical remission state was fulfillment of Definition Of Remission In SLE (DORIS). In Padova and Cochin Clinics, at time of inclusion, a senior clinician classified each patient as presenting: (i) remission, (ii) mild, or (iii) moderate/severe disease activity. Derivation of the SLE-DAS cut-offs for disease activity categories was performed using ROC curve analysis against this expert clinical classification. Performance of these SLE-DAS categories of disease activity was assessed as compared with: (i) expert classification (in Cochin cohort); (ii) British Isles Lupus Assessment Group (BILAG) index (in BLISS-76). An index-based and a Boolean definition of remission were tested applying decision trees, using CHAID (chi-square automatic interaction detection) algorithm and their performance estimated.Results:We included 1190 SLE patients (221 in Padova, 150 in Cochin and 819 from BLISS-76 cohorts). In the derivation cohort, best SLE-DAS cut-off values for disease activity categories were: (i) remission, SLE-DAS≤2.08; (ii) mild activity, 2.087.10. Table 1 shows the performance of these SLE-DAS cut-offs. The SLE-DAS Boolean-based definition of remission (all SLE-DAS clinical items scores = 0 and prednisone ≤5mg/day) showed sensitivity and specificity of 100% in the derivation (Padova) and validation (Cochin) clinical cohorts. The SLE-DAS index-based definition of remission (SLE-DAS ≤2.08 and prednisone ≤5mg/day) presented sensitivity =100% and specificity =97.4% in the derivation and validation clinical cohorts. The SLE-DAS definitions of remission were fully substantiated by CHAID.Table 1.Performance of SLE-DAS cut-offs for remission and disease activity categories compared to physician’s classification and BILAG (n =1190).Disease activity categorySensitivity (%)Specificity (%)Accuracy (%)DerivationPadova CohortRemission(SLE-DAS≤2.08)99.397.198.6Mild Disease Activity(2.0874.298.995.5Moderate and Severe Disease Activity(SLE-DAS>7.10)97.496.796.8ValidationCochin CohortRemission(SLE-DAS≤2.08)99.193.998.0Mild Disease Activity(2.0882.699.296.7Moderate and Severe Disease Activity(SLE-DAS>7.10)100.098.698.7ValidationBLISS-76Remission and Mild Disease Activity§vs. Moderate and Severe Disease Activity§§ (SLE-DAS≤7.10 vs. >7.10)91.484.190.8§ Remission/Mild: No BILAG B or A scores§§ Moderate/severe: ≥1 BILAG B or A scoresConclusion:The SLE-DAS is an accurate and easy to use tool for defining clinical remission state and SLE disease activity categories, validated with both the expert assessment and BILAG.References:[1]Jesus D, et al. Derivation and validation of the SLE Disease Activity Score (SLE-DAS): a new SLE continuous measure with high sensitivity for changes in disease activity. Ann Rheum Dis 2019;78:365-71.Acknowledgements:The authors would like to thank GlaxoSmithKline (Uxbridge, UK) for granting access to the data from the BLISS-76 trial through the Clinical Study Data Request consortium.Disclosure of Interests:None declared