Systemic lupus erythematosus (SLE) is a chronic autoimmune disease and hypocomplementemia signifies disease activity. Several studies have shown that calcium may help maintain optimum function of immune system and metabolism in SLE. The aim of our study was to analyze the relationship between total serum calcium level and SLE activity. A total of 66 patients with SLE and 214 healthy controls were included in this study. Our results showed lower serum levels of calcium (P < .001), complement C3 (P < .001), complement C4 (P < .001), and albumin (P < .001) in patients with SLE. A negative correlation was found between serum calcium level and systemic lupus erythematosus disease activity index (SLEDAI) rating (r = −0.394, P = .001). Additionally, serum level of calcium was positively correlated with serum complement C3 level (r = 0.366, P = .003) in patients with SLE, while no such correlation was found between serum calcium level and complement C4 (r = −0.190, P = .126). Likewise, patients with SLE with normal serum calcium level showed higher complement C3 level (P < .01) than that of patients with low serum calcium level. Overall, the results displayed that patients with SLE have lower serum calcium level compared to healthy controls, and the serum calcium level is positively correlated with SLEDAI rating and serum complement C3 level in patients with SLE. In conclusion, the total serum calcium level is negatively correlated with SLE disease activity.

系统性红斑狼疮 (SLE) 是一种慢性自身免疫性疾病，低补体血症意味着疾病活动。多项研究表明，钙可能有助于维持系统性红斑狼疮患者免疫系统和新陈代谢的最佳功能。我们研究的目的是分析总血清钙水平与 SLE 活动之间的关系。本研究共纳入 66 名 SLE 患者和 214 名健康对照者。我们的结果显示，SLE 患者的血清钙 ( P < .001)、补体 C3 ( P < .001)、补体 C4 ( P < .001) 和白蛋白 ( P < .001) 水平较低。血清钙水平与系统性红斑狼疮疾病活动指数（SLEDAI）评级之间存在负相关（r = -0.394，P = .001）。此外， SLE 患者的血清钙水平与血清​​补体 C3 水平呈正相关（r = 0.366，P = .003），而血清钙水平与补体 C4 之间没有发现这种相关性（ r = -0.190，P = .126）。同样，血清钙水平正常的 SLE 患者比血清钙水平低的患者表现出更高的补体 C3 水平 ( P < .01)。总体而言，结果显示，与健康对照相比，SLE患者的血清钙水平较低，并且SLE患者的血清钙水平与SLEDAI评分和血清补体C3水平呈正相关。总之，血清总钙水平与SLE疾病活动度呈负相关。