Association of Serum Sodium Levels with Inflammatory Markers and Disease Activity in Systemic Lupus Erythematosus: A Cross-sectional Study from a Tertiary Care Center in the Northern District of Kerala

Aim and background: Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder characterized by multisystem involvement.Ongoing inflammation is the key pathophysiological feature of SLE and can result in various systemic derangements.Hyponatremia is one such pathological derangement reported in SLE that could have serious clinical relevance.The aim is to study the association between hyponatremia in the SLE cohort with serum inflammatory markers [complement proteins (C3 and C4), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR)] and SLE disease activity index (SLEDAI) score.Materials and methods: Designed as a cross-sectional study involving 50 SLE patients from a tertiary care center in the Northern district of Kerala.Laboratory parameters evaluated in the study were serum sodium, C3, C4, CRP, and ESR.Serum sodium levels were correlated with inflammatory markers and SLEDAI score.Results: Systemic lupus erythematosus disease activity index score is 30.7 12.8, with 76, 10, and 14% having very high, moderate, and mild disease activity.The mean sodium level is 130 5.76 mEq/L, which is negatively correlated with the SLEDAI score (r = -0.36,p = 0.009).The mean C3 level in our study is 45 33.7 mg/dL, which positively correlated (r = 0.438, p = 0.001) with serum sodium levels.However, serum C4 (r = 0.025, p = 0.863), CRP (r = 0.177, p = 0.22), and ESR (r = -0.150,p = 0.299) did not show any statistically significant correlation with serum sodium. Conclusion:The study observed that hyponatremia significantly correlated with SLE disease activity and C3 levels.Plausibly, hyponatremia could be used as a marker for evaluating ongoing inflammation in SLE.Clinical significance: Diagnosing hyponatremia in SLE patients may indicate an ongoing inflammation and disease severity.Measuring serum sodium level is a non-invasive laboratory marker that could have an imperative role in the management of SLE.