Hyponatremia as an Inflammatory Marker of Lupus Activity Is a Fact or Fad: A Cross-Sectional Study

PURPOSE: Systemic lupus erythematosus (SLE) is an autoimmune disease with multi-organ involvement. Hyponatremia is common in inflammatory diseases such as meningitis. Also, it has been found to be strongly associated with the degree of inflammation. However, it has not been fully evaluated in lupus. This study aimed to assess the inflammatory impact of hyponatremia in SLE patients and investigate its relationship with SLE disease activity. PATIENTS AND METHODS: A total of 101 patients with SLE were enrolled in this study and divided into two groups according to Na level; a normo-natremic group and a hyponatremic group. Demographic and clinical data were collected. SLE activity was assessed by the systemic lupus erythematosus disease activity index (SLEDAI). The estimated sedimentation rate (ESR) as well as levels of C-reactive protein (CRP) and complements (C3 and C4) were measured. RESULTS: The majority of patients were females (98 subjects) (97%) with a mean age of 33±8 years. Out of 101 participants, 40 patients (39.6%) were hyponatremic with a mean Na level of 131.58±3.11 mmol/L. There was a statistically negative correlation between both ESR and SLEADI score and Na level (r=−0.436 and −0.436, respectively) with p=0.002, whereas Na level was positively correlated with complements, Cl, and albumin levels (r=0.653, 0.314, and 0.460, respectively) (p=0.000, 0.027, and >0.001, respectively). CRP was not correlated with Na level. ESR was independently correlated with hyponatremia at the 95% CI for Exp B (0.997–0.058) with a p-value of 0.048. CONCLUSION: Hyponatremia could be used as an indicator of SLE activity. Also, it might be an easily and rapidly detected as well as a prognostically useful marker of inflammation.