<h3>Background:</h3> Vitamin D (25OHD) has immunomodulatory properties that can play a major role in patients with active lupus or lupus nephritis. His immunomodulatory function could be influenced by demographic factors, comorbidities (Charlson score), bone supplements, and other features. <h3>Objectives:</h3> We explored the association between the best 25OHD cut-off points and specific clinical features that were present in patients with active lupus or lupus nephritis. <h3>Methods:</h3> A retrospective descriptive research using clinical registers of patients diagnosed with systemic erythematosus lupus, attended in two rheumatology clinics was performed. A decisions tree model was used to identify the best cut-off points of 25OHD [ng/mL] and clinical features associated with active lupus (SLEDAI-2k >6) or lupus nephritis. <h3>Results:</h3> We identified 81 patients, median age 41 years, women 91.3%. Active lupus and lupus nephritis were present in 69.1% and 29.6%, respectively. Median 25OHD was 26.49, without a difference at comparing with active lupus patients 24.85, but lower in lupus nephritis patients 21.50 (p: 0.015). Lupus nephritis was absent in patients with 25OHD cut-off points >38.8 (alone) or ≤38.8 if they were older than >57 years. Active lupus was always present in patients ≤44 years with <b>1.</b> High comorbidity or <b>2.</b> Low comorbidity plus cut-off point 25OHD >35; in >44 years, both a euthyroid state and the absence of bone supplements were present in patients with active lupus. <h3>Conclusion:</h3> Exist a strong relationship between vitamin D levels and LES activity. <h3>References</h3> [1] American College of Rheumatology. Guidelines for referral and management of systemic lupus erythematosus in adults. Arthritis Rheum. 1999 Sep;42(9):1785-96 [2] Simioni J, Heimovski F, Skare T. On lupus, vitamin D and leukopenia. 2016;56(3):206-211. [3] Guzman R.A, Piñeros L.G, Theran A, Flechas J, Mejía M. AB0795 Hypovitaminosis D and Calcium Intake of Adult Population in Bogota (DICAVITD). Ann Rheum Dis 2016;75:1175-. 1176. <h3>Acknowledgement:</h3> To Fundación Universitaria Juan N. Corpas <h3>Disclosure of Interests:</h3> None declared
