Serum glutathione reductase level as a disease activity biomarker in systemic lupus erythematosus: a single-centre preliminary study.

Objectives: This study aimed to investigate serum glutathione reductase (GR) levels in patients with SLE and to assess its association with disease activity.

Methods: The retrospective study collected clinical data, including serum GR, complement (C) 3 and C4 levels, among patients with SLE. The SLE Disease Activity Index 2000 (SLEDAI 2000) and SLE Disease Activity Score (SLE-DAS) were calculated, and C3 and C4 were used as controls to assess the importance of serum GR levels in evaluating SLE disease activity.

Results: Serum GR levels were significantly higher in patients with SLE (n=142) than in healthy controls (n=100). Serum GR levels were positively correlated with SLEDAI 2000 (ρ=0.335) and SLE-DAS (ρ=0.454) values in patients with SLE. Further, C3 and C4 were negatively correlated with SLEDAI 2000 (ρ = -0.544 and -0.418) and with SLE-DAS (ρ = -0.290 and -0.242). Fisher's Z test showed that GR was inferior to C3; however, similar to C4 in the correlation with SLEDAI 2000, whereas GR was comparable to C3 but superior to C4 in the correlation with SLE-DAS. The identification of moderate-to-severe disease activity based on SLEDAI 2000 of >6 revealed a receiver operating characteristic curve area under the curve (AUC) for GR of 0.700 (95% CI: 0.617 to 0.774), which was comparable to the AUC for C3 (0.784, 95% CI: 0.707 to 0.848) and C4 (0.697, 95% CI: 0.615 to 0.771); in determining moderate-to-severe disease activity as defined by SLE-DAS of >7.64, GR (0.767, 95% CI: 0.689 to 0.834) was equal to C3 (0.661, 95% CI: 0.576 to 0.738) but superior to C4 (0.617, 95% CI: 0.532 to 0.698).

Conclusion: Serum GR levels are positively correlated with SLE disease activity and exhibit clinical value in identifying moderate-to-severe disease activity in SLE.