Biochemistry, Antinuclear Antibodies (ANA)

The antinuclear antibody (ANA) is a defining feature of autoimmune connective tissue disease. ANAs are a class of antibodies that bind to cellular components in the nucleus, including proteins, DNA, RNA, and nucleic acid-protein complexes. First described in 1948, ANA testing has been the cornerstone of diagnosis for autoimmune connective tissue diseases, including systemic lupus erythematosus (SLE), Sjögren syndrome, and polymyositis/dermatomyositis. Although 20% to 30% of the general population has detectable ANA titers, higher titers are characteristic of individuals with connective tissue disorders. Thus, the sensitivity and specificity of the methods used to detect ANAs are crucial to diagnosis.