Urine β2-microglobulin is associated with clinical disease activity and renal involvement in female patients with systemic lupus erythematosus

Abstract

Objective We investigated the association of serum and urine β2-microglobulin (β2MG) with renal involvement and clinical disease activity in systemic lupus erythematosus (SLE). Methods Sixty-four female patients with SLE were enrolled. We assessed SLE disease activity (SLEDAI)-2K and measured serum and urine β2MG levels, as well as complement (C3 and C4) and anti-dsDNA levels. According to the SLEDAI scores, two groups were categorized: low (0–5 of SLEDAI) and high (6–19 of SLEDAI) disease activity groups. The presence of renal involvement was determined by renal SLEDAI score. Statistical analysis was performed using Spearman’s correlation analysis, Mann-Whitney U test, multivariate regression analysis, and logistic regression analysis. Results Urine β2MG levels were significantly different between low and high SLEDAI groups ( p = 0.001), but not for serum β2MG levels ( p = 0.579). Patients with renal involvement showed higher urine β2MG levels compared to those without renal involvement ( p < 0.001), but again there was not a difference in serum β2MG levels ( p = 0.228). Urine β2MG was closely associated with SLEDAI ( r = 0.363, p = 0.003), renal SLEDAI ( r = 0.479, p < 0.001), urine protein/Cr ( r = 0.416, p = 0.001), and ESR ( r = 0.347, p = 0.006), but not serum β2MG ( r = 0.245, p = 0.051). Urine β2MG level was identified as a surrogate for renal involvement ( p = 0.009, OR = 1.017, 95% CI 1.004–1.030) and overall disease activity ( p = 0.009, OR = 1.020, 95% CI 1.005–1.036). Conclusions We demonstrated that urine β2MG levels are associated with renal involvement and overall clinical disease activity in SLE.