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Background Vitamin D deficiency is frequent in SLE and may contribute to immune dysregulation. The relationship between vitamin D status and inflammatory markers such as NLR and PLR remains unclear.Objectives To assess the link between vitamin D deficiency and systemic inflammation in SLE (NLR, PLR, ESR, CRP), and its association with disease activity, organ damage, and clinical outcomes.Methods We conducted a cross-sectional study including 231 patients with SLE meeting the 2019 EULAR/ACR criteria. Eligible patients had recent results for blood count, 25(OH) vitamin D, ESR, and CRP obtained during a stable clinical visit. Group differences were analyzed using Student’s t-test or Mann–Whitney U test, depending on normality. Correlations between vitamin D, NLR, PLR, ESR and CRP, were assessed with Spearman’s rank test and multivariable linear regression, adjusting for confounders. Statistical analyses were performed with STATA 17.0, with significance set at p<0.05.Results The description of the main demographic, clinical, comorbidity, and analytical variables, along with their association with vitamin D levels (treated as a continuous variable), is presented in table 1.Interestingly, there was an association between vitamin D and cumulative organ damage, with lower concentrations detected in patients with organ damage compared to those without (Mann–Whitney z=2.63, p=0.0084).Regarding inflammatory markers, vitamin D levels showed a significant negative correlation with ESR ( r= –0.17, p=0.034) and neutrophil count (r = –0.21, p=0.041).Finally, in the multivariable linear regression including age, sex, ESR, CRP, neutrophil-to-lymphocyte ratio, diabetes, and cumulative organ damage, lower vitamin D levels were independently associated with higher NLR (Beta = –0.041, p = 0.017), presence of diabetes (Beta = –0.532, p < 0.001), and greater organ damage (Beta = –0.177, p = 0.007). (table 2, figure 1). Neutrophil count was significant in univariate analysis; however, NLR was used in the multivariate model as it provides a more robust measure of systemic inflammation and avoids redundancy or collinearity with other inflammatory parameters.Abstract PO:02:031 Table 1Demographic and clinical characteristics of SLE patients and their association with serum vitamin D levelsAbstract PO:02:031 Table 2Multiple liner regression. Factors associated with lower vitamin DAbstract PO:02:031 Figure 1Vitamin D and its relationship with organ damage and NRLConclusions Low vitamin D levels in SLE were independently linked to higher NLR and greater organ damage, supporting its role as a marker of disease severity. Prospective studies are needed to confirm causality and assess therapeutic potential.