title: The prevalence of rheumatoid factor isotypes and anti-cyclic citrullinated peptides in Malaysian rheumatoid arthritis patients.
abstract: OBJECTIVE
  The purpose of this study is to compare the prevalence of rheumatoid factor (RF) isotypes and second generation anti-cyclic citrullinated peptides (anti-CCP) in Malaysian rheumatoid arthritis (RA) patients.
  
  
  METHODS
  In this cross-sectional study, 147 established RA patients from three ethnic groups were recruited from a major rheumatology clinic in Malaysia. Enzyme-linked immunosorbent assays (ELISA) for serum RF isotypes IgA, IgG and IgM as well as second-generation anti-CCP were performed and the prevalence of each auto-antibody was compared in the three ethnic groups.
  
  
  RESULTS
  The anti-CCP was the most prevalent auto-antibody in each of the ethnic groups, followed closely by RF IgM and RF IgG. Rheumatoid factor IgA was the least prevalent across all three ethnic groups. The anti-CCP-RF IgM combination provided the best test sensitivity. Seroprevalence of anti-CCP was strongly associated with the presence of each of the RF isotypes. The seroprevalence of RF and anti-CCP did not increase or decrease with advancing age, age at onset and disease duration.
  
  
  CONCLUSIONS
  When used alone, anti-CCP provides a diagnostic advantage over RF IgM on the basis of test sensitivity. Considering the high cost of the anti-CCP assay, step-wise serum testing with IgM RF followed by anti-CCP may provide a more economically sensible option to optimize test sensitivity for RA.
authors.affiliation: Pathology Division, Faculty of Medicine and Health, International Medical University, Kuala Lumpur, Malaysia.
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: Somnath
authors.forename: Beryl
authors.initials: B
authors.lastname: D'Souza
authors.forename: Ai Lee
authors.initials: AL
authors.lastname: Lim
authors.forename: Karuthan
authors.initials: K
authors.lastname: Chinna
authors.forename: Ammu K
authors.initials: AK
authors.lastname: Radhakrishnan
mesh_terms: D000293:Adolescent; D000328:Adult; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000208:ethnology / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D002681:China / Q000208:ethnology; D005260:Female; D006801:Humans; D007132:Immunoglobulin Isotypes / Q000097:blood; D007194:India / Q000208:ethnology; D008296:Malaysia / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012217:Rheumatoid Factor / Q000097:blood / Q000276:immunology*; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D000888:Antibodies, Anti-Idiotypic; D001323:Autoantibodies; D007132:Immunoglobulin Isotypes; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor