Antinuclear Antibody (ANA)

Figure 3.31 ANA patterns A: Homogenous* B: Nucleolar* C: Centromeric* *Reprint from Cuenca S, et al. Rationelle und rationale Laboratorium diagnostik in der Hals-Nasen-Ohren-Heilkunde. HNO. 2008: 56 (9); 855–73 D: Speckled (Reprint from Vergani D, et al. Autoimmune Hepatitis. Seminars in Immunopathology. 2009: 31 (3); 421–435)

• Family of autoantibodies which may be directed at one or several of the following nuclear antigens:
  • Extractable nuclear antigens (ENAs)
    • Sm (Smith)
    • RNP (U1 ribonucleoprotein)
    • Ro (SSA)
    • La (SSB)
    • Scl-70
    • Jo-1
  • Non-ENAs
    • ds-DNA (double stranded)
    • Histone
    • Nuclear RNA
• ANA assay measures the amount (titer) and pattern of antibodies in a patient’s serum that bind autoantigens present in the nucleus of cells
• The titer represents the last doubling dilution in order to produce a sample with no fluorescence (ANA-free)
• Two types of assays: indirect IF (IIF) and ELISA
  • IIF: most accurate, uses Hep-2 epithelial carcinoma cells as substrate (due to ↑ nuclear/cytoplasmic ratio)
  • ELISA: more popular due to decreased cost
• Patterns of nuclear fluorescence if ANA titer positive:
  • Homogenous (diffuse) suggests anti-dsDNA (SLE)
  • Peripheral (rim) suggests anti-dsDNA (SLE)
  • Speckled suggests anti-U1RNP (MCTD, Sjögren)
  • Centromeric stains kinetochore (CREST)
  • Nucleolar suggests anti-fibrillarin (SSc)
• Five percent of normal population with elevated ANA but nonsignificant; ANA increases with age (i.e. 15% patients >55 years of age with ↑ ANA titer but no clinical significance)