title: 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.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Arthritis & Autoimmunity Research Center, Catholic University of Daegu School of Medicine, Daegu, Republic of Korea.
authors.forename: J-Y
authors.initials: JY
authors.lastname: Choe
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Arthritis & Autoimmunity Research Center, Catholic University of Daegu School of Medicine, Daegu, Republic of Korea.
authors.forename: S-H
authors.initials: SH
authors.lastname: Park
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Arthritis & Autoimmunity Research Center, Catholic University of Daegu School of Medicine, Daegu, Republic of Korea kimsk714@cu.ac.kr.
authors.forename: S-K
authors.initials: SK
authors.lastname: Kim
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine*; D001799:Blood Sedimentation; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000150:complications / Q000652:urine*; D008181:Lupus Nephritis / Q000097:blood / Q000209:etiology / Q000652:urine; D008875:Middle Aged; D012720:Severity of Illness Index; D001613:beta 2-Microglobulin / Q000097:blood / Q000652:urine*
chemical_list: D015415:Biomarkers; D001613:beta 2-Microglobulin; D003404:Creatinine
keywords: disease activity; renal involvement; systemic lupus erythematosus; β2-microglobulin