title: Comparison of anti-agalactosyl IgG antibodies, rheumatoid factors, and anti-cyclic citrullinated peptide antibodies in the differential diagnosis of rheumatoid arthritis and its mimics.
abstract: OBJECTIVE
  Anti-agalactosyl IgG antibodies [anti-Gal(0) IgG] have been regarded as a useful serological marker for rheumatoid arthritis (RA). Our aim was to evaluate the clinical usefulness of anti-Gal(0) IgG in the differential diagnosis of rheumatic disorders that mimic RA compared to rheumatoid factors (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP).
  
  
  METHODS
  Sera were collected from 39 patients with RA, 49 patients with primary Sjögren's syndrome (pSjS), 47 patients with systemic lupus erythematosus (SLE), 65 patients with chronic hepatitis B viral infection (HBV), 68 patients with chronic hepatitis C viral infection (HCV) and 19 normal individuals. RF-IgM was measured by the nephelometeric method, and RF-IgA, anti-Gal(0) IgG and anti-CCP were measured by the respective ELISA assays.
  
  
  RESULTS
  Anti-Gal(0) IgG titers were remarkably elevated in patients with RA (191.0 +/- 250.8 AU/ml) compared to pSjS (37.9 +/- 42.6 AU/ml), SLE (10.3 +/- 13.6 AU/ml), chronic HBV with (36.1 +/- 38.4 AU/ml) or without rheumatic symptoms (9.6 +/- 19.4 AU/ml), RF(+) chronic HCV without rheumatic symptoms (19.0 +/- 14.8 AU/ml), chronic HCV with rheumatic symptoms (15.2 +/- 17.4 AU/ml) and healthy individuals (2.6 +/- 0.7 AU/ml). The specificity of anti-Gal(0) IgG could be greatly enhanced by elevating the cut-off value from 12 AU/ml to 40 AU/ml (68.6% vs. 85.6%, p < 0.001) without significantly compromising its sensitivity (76.9% vs. 61.5%, p > 0.05).
  
  
  CONCLUSIONS
  The serum titer of anti-Gal(0) IgG is much higher in rheumatoid arthritis than in mimicking diseases. The specificity of anti-Gal(0) IgG is enhanced when the cut-off value is raised. However, anti-CCP remains the most specific biomarker for RA.
authors: Division of Immunology, Rheumatology and Allergy, Buddhist Dalin Tzu-Chi General Hospital, Chia-Yi, Taiwan.
authors: M-C
authors: MC
authors: Lu
authors: S-C
authors: SC
authors: Hsieh
authors: N-S
authors: NS
authors: Lai
authors: K-J
authors: KJ
authors: Li
authors: C-H
authors: CH
authors: Wu
authors: C-L
authors: CL
authors: Yu
mesh_terms: D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D003937:Diagnosis, Differential; D005260:Female; D006509:Hepatitis B / Q000175:diagnosis / Q000276:immunology; D006526:Hepatitis C / Q000175:diagnosis / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012217:Rheumatoid Factor / Q000276:immunology*; D012680:Sensitivity and Specificity; D012859:Sjogren's Syndrome / Q000175:diagnosis / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D015415:Biomarkers; D007074:Immunoglobulin G; D010456:Peptides, Cyclic; C064155:agalactosyl IGG; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor