Anti-RA 33 antinuclear autoantibody in rheumatoid arthritis and mixed connective tissue disease: comparison with antikeratin and antiperinuclear antibodies

Clin Exp Rheumatol. 1993 Sep-Oct;11(5):473-8.


Besides rheumatoid factor (RF), antikeratin antibodies (AKA) and antiperinuclear factor (APN), anti-RA 33 antibody has been described as a highly specific antinuclear antibody for rheumatoid arthritis (RA). In this study RA 33 antibodies were detected using Western blotting with HeLa cell nuclear extract in a group of 94 RA patients and 259 controls. Anti-RA 33 was present in 35% of 94 RA patients, with a similar frequency in RF positive (32%) and RF-negative (45%) RA patients. RA-33 antibody was also present in 60% of a group of 30 patients with anti-U1 RNP positive mixed connective tissue disease. The specificity of anti-RA 33 for RA was 84.6%. Anti-RA 33 antibody was already present in sera from 23.5% of 18 patients with RA of less than one year's duration. Anti-RA 33 antibody was the only positive immunological marker in 3/20 cases of seronegative adult RA. No correlations were found between anti-RA 33 antibody and AKA or APF. Patients with erosive RA and patients whose ESR was > or = 50 mm after 1 hour were more likely to be anti-RA 33 positive (47.6% vs 24.4% and 42.8% vs 29.4%). These results suggest that anti-RA 33 antibody, in the absence of anti-U1-RNP antibodies, can be added to the list of the helpful serological markers for rheumatoid arthritis.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Antineutrophil Cytoplasmic
  • Antibodies, Antinuclear / blood*
  • Arthritis, Rheumatoid / diagnosis
  • Arthritis, Rheumatoid / immunology*
  • Autoantibodies / blood*
  • Biomarkers / blood
  • Diagnosis, Differential
  • Female
  • Humans
  • Keratins / immunology
  • Male
  • Middle Aged
  • Mixed Connective Tissue Disease / diagnosis
  • Mixed Connective Tissue Disease / immunology*
  • Sensitivity and Specificity


  • Antibodies, Antineutrophil Cytoplasmic
  • Antibodies, Antinuclear
  • Autoantibodies
  • Biomarkers
  • Keratins