title: Relatives without rheumatoid arthritis show reactivity to anti-citrullinated protein/peptide antibodies that are associated with arthritis-related traits: studies of the etiology of rheumatoid arthritis.
abstract: OBJECTIVE
  To examine reactivity to anti-citrullinated protein/peptide antibodies (ACPAs) and determine associations between ACPAs and other rheumatoid arthritis (RA)-related autoantibodies and clinically assessed swollen or tender joints in unaffected first-degree relatives of RA patients.
  
  
  METHODS
  Serum samples were obtained from first-degree relatives without RA according to the 1987 American College of Rheumatology (ACR) and the 2010 ACR/European League Against Rheumatism classification criteria. A bead-based assay was used to measure 16 separate ACPAs in sera from 111 antibody-positive first-degree relatives who were positive on at least 1 visit for any of 5 RA-related autoantibodies (rheumatoid factor [RF], anti-cyclic citrullinated peptide 2 [anti-CCP-2], and RF isotypes), and sera from 99 antibody-negative first-degree relatives who were never autoantibody positive. Cutoffs for positivity for each ACPA were determined using receiver operating characteristic curves derived from data on 200 RA patients and 98 blood donor controls, in which positivity for ≥9 ACPAs had 92% specificity and 62% sensitivity for RA. In first-degree relatives, ACPA reactivity was assessed, and associations between ACPAs (number positive, and positivity for ≥9 ACPAs) and RA-related characteristics were examined.
  
  
  RESULTS
  Fifty-seven percent of anti-CCP-2-positive first-degree relatives and 8% of anti-CCP-2- negative first-degree relatives were positive for ≥9 ACPAs. After adjusting for age, sex, ethnicity, and pack-years of smoking, an increasing number of ACPAs was directly associated with the presence of ≥1 tender joint on examination (odds ratio [OR] 1.18, 95% confidence interval [95% CI] 1.04-1.34), with the greatest risk of having ≥1 tender joint seen in first-degree relatives positive for ≥9 ACPAs (OR 5.00, 95% CI 1.37-18.18).
  
  
  CONCLUSIONS
  RA-free first-degree relatives (even those negative for RF and anti-CCP-2) demonstrate reactivity to multiple ACPAs, and the presence of an increasing number of ACPAs may be associated with signs of joint inflammation. Prospective evaluation of the relationship between these findings and the progression of classifiable RA is warranted.
authors.affiliation: Colorado School of Public Health, Aurora, CO, USA.
authors.forename: Kendra A
authors.initials: KA
authors.lastname: Young
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Deane
authors.forename: Lezlie A
authors.initials: LA
authors.lastname: Derber
authors.forename: Jan M
authors.initials: JM
authors.lastname: Hughes-Austin
authors.forename: Catriona A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sokolove
authors.forename: Michael H
authors.initials: MH
authors.lastname: Weisman
authors.forename: Jane H
authors.initials: JH
authors.lastname: Buckner
authors.forename: Ted R
authors.initials: TR
authors.lastname: Mikuls
authors.forename: James R
authors.initials: JR
authors.lastname: O'Dell
authors.forename: Richard M
authors.initials: RM
authors.lastname: Keating
authors.forename: Peter K
authors.initials: PK
authors.lastname: Gregersen
authors.forename: William H
authors.initials: WH
authors.lastname: Robinson
authors.forename: V Michael
authors.initials: VM
authors.lastname: Holers
authors.forename: Jill M
authors.initials: JM
authors.lastname: Norris
mesh_terms: D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D005190:Family; D005192:Family Health; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007596:Joints / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide