Evaluation of Complement (C3d) as Urinary Immune-Related Biomarker in the Diagnosis of Lupus Nephritis

Abstract

Background: Kidney involvement is a key problem in systemic lupus erythematosus (SLE), affecting about 50% of patients and responsible for a large amount of morbidity and mortality. Early identification and treatment can significantly alter the course of renal illness and enhance long-term survival. This study aimed to evaluate the diagnostic value of Complement 3d as urinary immune-related biomarker for the diagnosis of lupus nephritis in patients of SLE. Methods: A cross sectional study on 78 patients with SLE (72 females and 6 males) was conducted from September 2021 to March 2022. Renal involvement was determined using the renal SLEDAI, which incorporates the SLEDAI-2k kidney-related parameters: "hematuria, pyuria, proteinuria, and urinary casts." Results: Urinary complement 3d levels were statistically higher in the LN group than those without LN (p value <0.000). Levels of urinary C3d positively correlated with renal SLEDAI. Conclusions: This study concluded that urinary C3d had a high accuracy and can be considered a good predictor for the diagnosis of active LN in SLE patients, and C3d can be used to evaluate nephritis activity in SLE patients.