title: Circulating leptin level in rheumatoid arthritis and its correlation with disease activity: a meta-analysis.
abstract: OBJECTIVE
  This study aimed to evaluate the relationship between the circulating serum leptin level and rheumatoid arthritis (RA) and to establish a correlation between serum leptin levels and RA activity.
  
  
  METHODS
  We searched the PUBMED, EMBASE, and Cochrane databases. A meta-analysis was performed, comparing the serum/plasma leptin levels in patients with RA and healthy controls. Correlation coefficients between serum leptin level and either disease activity score 28 (DAS28) or C‑reactive protein (CRP) in RA patients were also examined.
  
  
  RESULTS
  Thirteen studies with a total of 648 RA patients and 426 controls were included in this meta-analysis. Circulating leptin level was significantly higher in the RA group than in the control group (SMD = 1.056, 95 % CI = 0.647-1.465, p = 4.2 × 10-7). In addition, stratification by ethnicity showed a significantly elevated leptin level in the RA group in Caucasian, Turkish, and Arab populations (SMD = 0.813, 95 % CI = 0.137-1.490, p = 0.018, SMD = 0.981, 95 % CI = 0.307-1.655, p = 0.004, and SMD = 1.469, 95 % CI = 0.443-2.495, p = 0.005 respectively). A meta-analysis of correlation coefficients showed a small but significantly positive correlation between the circulating leptin level and either DAS28 (correlation coefficient = 0.275, 95 % CI = 0.076-0.452, p = 0.007) or CRP (correlation coefficient = 0.274, 95 % CI = 0.068-0.458, p = 0.010).
  
  
  CONCLUSIONS
  Our meta-analysis demonstrated that the circulating leptin level is significantly higher in patients with RA and that a small but significantly positive correlation exists between leptin levels and RA activity.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, 73, Inchon-ro, Seongbuk-gu, 136-705, Seoul, Korea. lyhcgh@korea.ac.kr.
authors.forename: Y H
authors.initials: YH
authors.lastname: Lee
authors.affiliation: Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Seoul, Korea.
authors.forename: S-C
authors.initials: SC
authors.lastname: Bae
mesh_terms: D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology; D015415:Biomarkers / Q000097:blood; D018450:Disease Progression; D006801:Humans; D020738:Leptin / Q000097:blood*; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013223:Statistics as Topic
chemical_list: D015415:Biomarkers; D020738:Leptin
keywords: Activity; Correlation; Leptin; Meta-analysis; Rheumatoid arthritis
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