title: [Specific antibodies for the early diagnosis of rheumatoid arthritis].
abstract: OBJECTIVE
  To assess the specificity and sensitivity of antiperinuclear factor (APF), anti-keratin antibody (AKA), anti-Sa antibody and anti-RA33 antibody in the diagnosis of RA.
  
  
  METHODS
  128 patients with RA, whose durations were within 1 year, were included. APF and AKA were detected by indirect immunofluorescence on the human buccal mucosa cells and the straum corneum of Wistar rat esophagus. Anti-Sa antibody and anti-RA33 antibody were examined by Western blotting. Sa antigen was extracted from human placenta while RA33 antigen from Ehrlich cells.
  
  
  RESULTS
  (1) The specificities and sensitivities of APF, AKA, anti-Sa antibody and anti-RA33 antibody were 91.4% (224/245) & 35.2% (45/128), 90.2% (221/245) & 32.0% (43/128), 90.6% (222/245) & 33.6% (43/128), 89.8% (220/245) & 28.9% (37/128), respectively, versus 72.3% (177/245) & 44.5% (57/128) for rheumatoid factor (RF). There were no statistical differences in the specificity between the four antibody groups and RF until 1:128 were taken as positive titer. Among 71 patients with RF-negative RA, 15 (21.1%) were positive for APF, 18 (25.4%) positive for AKA, 21 (29.6%) positive for anti-Sa antibody and 17 (23.9%) positive for anti-RA33 antibody. (2) Specificity and sensitivity were 95.1% (233/245) and 46.1% (59/128) respectively when two of the four antibodies turned out to be both positive. If three or more kinds were detected simultaneously, specificity was as much as 99.6% (108/128). (3) Statistical difference was found among the four groups defined by the number of positive antibodies in radiographic stage and patients assessment of illness.
  
  
  CONCLUSIONS
  (1) Dictation of APF, AKA, anti-Sa antibody and anti-RA33 antibody can greatly improve the specificity of diagnosis of early RA and serve as a complement when RF is negative. (2) Combined detection of the above four antibodies has a better discrimination ability as a laboratory criterion than that of RF. (3) Three or more positive antibodies may be an indicator of severe bone erosion and emergent demand for early treatment with better outcome.
authors.affiliation: Department of Rheumatology and Immunology, Peking Union Medical College Beijing 100730, China.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: X
authors.initials: X
authors.lastname: Gan
mesh_terms: D000209:Acute-Phase Proteins / Q000276:immunology*; D000328:Adult; D000368:Aged; D000818:Animals; D000974:Antibodies, Antinuclear / Q000032:analysis*; D000918:Antibody Specificity; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology; D003066:Coenzyme A Ligases; D005260:Female; D006801:Humans; D007633:Keratins / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D011506:Proteins / Q000276:immunology*; D051381:Rats; D017208:Rats, Wistar; D012217:Rheumatoid Factor / Q000276:immunology; D012698:Serologic Tests
chemical_list: D000209:Acute-Phase Proteins; D000974:Antibodies, Antinuclear; D011506:Proteins; C030902:antiperinuclear factor; C048262:rheumatoid arthritis specific protein, human; D007633:Keratins; D012217:Rheumatoid Factor; C081817:Acsm3 protein, rat; D003066:Coenzyme A Ligases