title: Elevated serum glucose-6-phosphate isomerase correlates with histological disease activity and clinical improvement after initiation of therapy in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  To determine serum glucose-6-phosphate isomerase (GPI) concentrations in patients with rheumatoid arthritis (RA), and to test whether they correlate with objective measures of disease activity.
  
  
  METHODS
  Sera from 116 patients with RA, 69 patients with non-RA rheumatic diseases, and 101 healthy controls were analyzed. Levels of soluble serum GPI were measured by ELISA. Histological disease activity was determined with the synovitis score in synovial needle biopsies from 58 of the 116 patients with RA. Thirty-one of the 58 synovium samples were stained for CD68, CD3, CD20, CD38, CD79a, and CD34 by immunohistochemistry. Demographic data were collected, as well as serological and clinical variables that indicate RA disease activity, for Spearman correlation analysis.
  
  
  RESULTS
  Serum GPI level correlated positively with the synovitis score (r = 0.278, p = 0.034). Significantly higher soluble GPI levels were detected in the RA sera compared with sera from healthy controls and the non-RA disease controls (2.25 ± 2.82 vs 0.03 ± 0.05 and 0.19 ± 0.57 μg/ml, respectively; p < 0.0001). The rate of serum GPI positivity was significantly higher in the RA patients than in the non-RA disease controls (64.7% vs 10.1%; p < 0.0001). Spearman analysis showed no significant correlation between serum GPI level and Disease Activity Score in 28 joints at baseline. After initiation of antirheumatic treatments, GPI levels decreased significantly (2.81 ± 3.12 vs 1.44 ± 2.09 μg/ml; p = 0.016), paralleling improvement of the disease activity indices.
  
  
  CONCLUSIONS
  Elevated serum GPI may be involved in the synovitis of RA and may prove useful as a serum marker for disease activity of RA.
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, P.R. China. liedai2004@hotmail.com
authors.forename: Lie
authors.initials: L
authors.lastname: Dai
authors.forename: Lang-Jing
authors.initials: LJ
authors.lastname: Zhu
authors.forename: Dong-Hui
authors.initials: DH
authors.lastname: Zheng
authors.forename: Ying-Qian
authors.initials: YQ
authors.lastname: Mo
authors.forename: Xiu-Ning
authors.initials: XN
authors.lastname: Wei
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Su
authors.forename: Frank
authors.initials: F
authors.lastname: Pessler
authors.forename: Bai-Yu
authors.initials: BY
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy / Q000201:enzymology* / Q000503:physiopathology*; D015415:Biomarkers / Q000378:metabolism; D002648:Child; D005260:Female; D005956:Glucose-6-Phosphate Isomerase / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013582:Synovial Fluid / Q000276:immunology; D013585:Synovitis / Q000097:blood / Q000276:immunology / Q000473:pathology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D005956:Glucose-6-Phosphate Isomerase