Antinuclear antibodies

Diseases commonly associated with a positive Antinuclear Antibody test

Even among normal blood donors the incidence of a positive ANA is approximately 5% when the screening is done with a serum dilution of 1:40. However, these false positive ANA's are usually of low titre and less that 1% of the normal population will have a titre of > or = 1:160.

Usually the titre of the ANA test is >1:160 in the systemic connective tissue diseases. But neither the disease activity nor the patient's prognosis can be related to the titre of the ANA.

Approximately 5% of patients with rheumatoid arthritis are ANA positive and rheumatoid factor negative. These patients seem to behave clinically like rheumatoid factor positive patients.

ANA patterns seen with indirect immunofluorescent staining of HEP 2 cells

• Homogenous: drug induced SLE and RA
• Speckled:
  • with anti- RNP antibodies found in patients with mixed connective disease
  • with anti-SM antibodies found in patients with SLE
  • with other less well-characterized anti-nuclear antibodies found in scleroderma and polymyositis
• Centromere: seen with anti- centromere antibodies found specifically in patients with CREST syndrome
• Nucleolar: seen with antibodies to ribonuclear proteins and RNA polymerases found primarily in patients with scleroderma.

Drug-induced lupus

• Brad Cheek: last updated Dec 2006
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