title: Ethnic differences in the prognostic utility of rheumatoid factor isotypes and anticyclic citrullinated peptides in rheumatoid arthritis patients: a cross-sectional study.
abstract: OBJECTIVE
  The prognostic significance of rheumatoid factor (RF) and anticyclic citrullinated peptide antibody (anti-CCP) in rheumatoid arthritis (RA) remains contentious due to the conflicting lines of evidence. This study aims to determine the association between RF isotypes and anti-CCP with disease severity in RA patients from three ethnic groups.
  
  
  METHODS
  A total of 147 RA patients from three different ethnic groups (Malays, Chinese, and Indians) who fulfilled the 1987 American College of Rheumatology (ACR) revised criteria for RA were recruited into this study. The seroprevalence of RF isotypes immunoglobulin (Ig)A, IgG, and IgM, as well as anti-CCP was determined using commercial enzyme-linked immunosorbent assay (ELISA) kits. Multinomial regression analysis was performed to assess the independent effects of autoantibody status on the development of deforming and erosive RA and the presence of extra-articular manifestations (EAM).
  
  
  RESULTS
  In Chinese patients, we found a significant association (p < 0.05) between IgG RF and anti-CCP and the presence of erosive disease, as well as IgM RF and IgG RF with the presence of joint deformities. In Indian patients, IgM RF was associated with deforming disease, whereas none of the antibodies were associated with disease severity in Malay patients. Multinomial regression analysis revealed that IgG RF was the most important predictor variable for erosive disease in Chinese patients, and IgM RF the only predictor variable associated with deforming disease in both Chinese and Indian RA patients.
  
  
  CONCLUSIONS
  There is variability in the phenotypic association of RF isotypes and anti-CCP in relation to disease severity of RA in the three ethnic groups. RF, in particular, IgG and IgM, may be better prognosticators of severe disease in Chinese and Indian patients.
authors.affiliation: International Medical University, No: 126 Jalan Jalil Perkasa 19/155B, Bukit Jalil, 57000 Kuala Lumpur, Malaysia. Edmund_Gomez@health.qld.gov.au
authors.forename: Edmund Luke
authors.initials: EL
authors.lastname: Gomez
authors.forename: Suk Chyn
authors.initials: SC
authors.lastname: Gun
authors.forename: Sushela Devi
authors.initials: SD
authors.lastname: Somanath
authors.forename: Karuthan
authors.initials: K
authors.lastname: Chinna
authors.forename: Ammu K
authors.initials: AK
authors.lastname: Radhakrishnan
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000208:ethnology / Q000276:immunology*; D001323:Autoantibodies / Q000032:analysis*; D002681:China / Q000208:ethnology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007194:India / Q000208:ethnology; D008296:Malaysia / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D011379:Prognosis; D012217:Rheumatoid Factor / Q000276:immunology*; D016036:Seroepidemiologic Studies; D012720:Severity of Illness Index
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor