title: Superior specificity of anti-citrullinated peptide antibodies in patients with chronic lymphocytic leukemia and arthritis.
abstract: OBJECTIVE
  Sera from patients with lymphoid neoplasias contain rheumatoid factors (RF) so often that RF are of limited use for diagnosing arthritis in lymphoma patients. Antibodies against citrullinated peptides (ACPA) might be helpful in distinguishing between true RA and rheumatoid factor-positive conditions with arthritis. We compared the specificity of RF and of ACPA for the diagnosis of RA in patients with B-cell chronic lymphocytic leukemia (CLL).
  
  
  METHODS
  One hundred and seven patients with CLL without any clinical signs of arthritis and five patients with RA and concomitant CLL were included in the investigation. Serum samples were tested for RF-isotypes IgM, IgG and IgA. ACPA were determined with an ELISA that detects anti-cyclic citrullinated peptide (aCCP) antibodies.
  
  
  RESULTS
  RF well beyond the cut-off levels were detected in 50% of the CLL patients without RA. The isotype distribution was 41% IgM-RF, 20% IgG-RF and 3% IgA-RF. None of the 107 CLL patients without arthritis had Accp antibodies. Within the whole cohort of CLL patients the specificity for the diagnosis of RA was 100% for aCCP antibodies and 59% for IgM-RF.
  
  
  CONCLUSIONS
  Only aCCP antibodies but not IgM-, IgG- or IgA-RF are useful for the diagnosis of RA in patients with CLL.
authors.affiliation: Division of Rheumatology and Immunology, Department of Internal Medicine, Medical University Graz, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Brickmann
authors.forename: R I
authors.initials: RI
authors.lastname: Brezinschek
authors.forename: B
authors.initials: B
authors.lastname: Yazdani-Biuki
authors.forename: W B
authors.initials: WB
authors.lastname: Graninger
authors.forename: H-P
authors.initials: HP
authors.lastname: Brezinschek
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000888:Antibodies, Anti-Idiotypic / Q000097:blood* / Q000276:immunology; D000918:Antibody Specificity; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood / Q000150:complications* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012217:Rheumatoid Factor / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D000888:Antibodies, Anti-Idiotypic; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor