Antinuclear antibodies $$$

ANA are the antibodies (gamma globulins) important for diagnostics; they include all autoantibodies against nuclear antigens in the cell nucleus and cytoplasm. In contrast to the original definition, the term "ANA" also includes antibodies against cytoplasmic and mitochondrial target antigens. ANA include, for example, DNA, histones (H1, H2A, H2B, H3, H4), DNA-histone complexes, ribonucleoproteins (U1-RNP, Sm, La (SS-A), Ro (SS-B), Jo-1 (histidyl-t-RNA transferase)), and non-histone proteins (centromere-AK, Scl-70, PM-1, Mi-2).

See also Autoantibodies.

Extractable antinuclear antibodies(ENA) form a diagnostically important subgroup.

Detection by indirect immunofluorescence methods (considered the gold standard); HEp-2 cells form the substrate. The fluorescence pattern gives an indication of the specificity of the antibody. Nuclear, cytoplasmic and mitotic patterns are distinguished. Diagnosis is performed according to ICAP, an international standard (ICAP = International Consensus on Antinuclear Antibody Pattern), which distinguishes 20 discrete fluorescence patterns (ICAP code).

Furthermore, ELISA techniques as well as immunoblot procedures(Western blot) can be used.

Standard value: The standard value is positive from a titer of 1: 160 (ANA with low affinity is often detected in healthy people).

Pathologically elevated: Felty syndrome, systemic lupus erythematosus, autoimmune hepatitis, drug-induced discoid and subacute cutaneous lupus erythematosus, systemic sclerosis, multiple non-inflammatory diseases, juvenile chronic arthritis, poly-/dermatomyositis.

Positive findings in older people without detectable disease (frequency varies according to literature. Up to 30% in people > 60 years; up to 8% in people <60 years).

• Diseases in which ANA determination is important for diagnosis/progress control:
  • Systemic lupus erythematosus (95-100%)
  • Drug-induced LE (95-100%)
  • Congenital lupus erythematosus
  • Systemic Scleroderma
  • Polymyositis (mostly Jo-1 positive)
  • Dermatomyositis (mostly Jo-1 positive)
  • Primary Sjögren's syndrome (mostly SS-A (Ro) and SS-B-(La) positive
  • Mixed Connective Tissue Disease (mostly RNP-positive, typically in high concentrations).
  • CREST syndrome (usually centromer-positive).
• ANA may be present as an accompanying phenomenon; they have no diagnostic value in the following diseases:
  • Chronically active hepatitis (especially hepatitis C)
  • Polyarthritis, chronic (rheumatoid arthritis) ("rheumatism")
  • Arthritis, psoriatic
  • Felty syndrome (60-95%)
  • Haemolytic anaemia (50%)
  • Juvenile chronic arthritis
  • Rheumatoid arthritis ( 20-50% )
  • Polyarteritis nodosa, systemic (20%)
  • Pulmonary fibrosis (fibrosing alveolitis)
  • myasthenia gravis
  • Primary biliary cirrhosis (40%)
  • alcoholic toxic liver cirrhosis (30%)
  • autoimmune hepatitis (60-100%)
  • viral hepatitis (30%)
  • malaria (30%)
  • leukemias (30-70%)
  • Sarcoidosis.