Clinical value of combined serum galectin-9 and urine MCP-1 testing for assessment of systemic lupus erythematosus disease activity and early diagnosis of lupus nephritis.

OBJECTIVES

To investigate whether combined measurement of serum galectin-9 and urinary monocyte chemoattractant protein-1 (MCP-1) can serve as non-invasive biomarkers for assessing disease activity in systemic lupus erythematosus (SLE) and for the early identification of lupus nephritis (LN).

METHODS

This retrospective study included 148 SLE patients hospitalized between June 2022 and May 2025. Patients were divided into three groups: inactive SLE group (n=48), active SLE without LN group (n=40), and active SLE with LN group (n=60). Serum galectin-9, urinary MCP-1, and routine indices (e.g., complement levels, autoantibodies) were measured at admission.

RESULTS

Serum markers increased progressively with disease progression: galectin-9 levels (8.59 ± 0.63 vs. 9.68 ± 1.87 vs. 11.72 ± 2.14 ng/mL) and urinary MCP-1 levels (1.58 ± 0.42 vs. 2.85 ± 0.92 vs. 10.45 ± 3.18 pg/mg creatinine, all P<0.05). Correlation analysis showed that both biomarkers were associated with SLE disease activity (both P<0.05). Regarding the diagnosis of LN, the area under the curve (AUC) was 0.782 for galectin-9 and 0.796 for MCP-1. Combined detection further improved diagnostic performance, yielding an AUC of 0.866. Moreover, urinary MCP-1 levels were significantly higher in patients with proliferative LN than in those with non-proliferative LN (12.36 ± 3.28 vs. 8.25 ± 2.84 pg/mg creatinine; P<0.001).

CONCLUSIONS

Combined assessment of serum galectin-9 and urine MCP-1 provides a non-invasive approach for evaluating overall disease activity in SLE and may facilitate early identification of LN. Compared to traditional indicators, this strategy had superior diagnostic accuracy.