What is antinuclear antibody ANA ?
• It is any autoantibody directed against one or more components of the nucleus.• It is used to detect a disorder but not to rule out Connective Tissue disease as it can be + ve in other unrelated diseases.
Immunofluorescence microscopy after serum has been applied to a nucleated tissue substrate e.g (rodent organs) or human cell lines is the standard
method of detection giving different patterns of staining.
ANA patterns:
• Speckled pattern.
• Homogenous pattern.
• Nucleolar pattern.
• Causes of + ve ANA
1- SLE 95 -100%.2- Scleroderma 80 %.
3- Polymyositis 80 %.
4- Rheumatoid arthritis 30 %, Sjogren's disease 70 %.
5- Mixd connective tissue disease 95%. Sjogren's syndrome 60-70%.
6- Primary biliary cirrhosis, autoimmune hepatitis .
7- Normal elderly people, infective endocarditis.
The results of ANA can be expressed by a titre. AUtre of 1:40 - 1:80 is considered positive, but 1:160 is significant.
If ANA is positive, it is important to ask about specific antibodies (ANA profile ).
Other specific antibodies or specific antinuclearantibodies (ANA profile)
i.e tests that measure ANAs specific for certain nuclear antigens.1- Anti-double stranded DNA (antinative DNA).
• It is specific for S L E.• It determines the activity of the disease, it is positive in about 40-75% of cases (negative in mild or inactive
disease). High titre indicates poor prognosis.
2- Antihistone antibody.
It is positive in drug induced SLE. (>90%)3- Anti-Smith Antibody. (anti-sm)
Directed against non histone nuclear protein, specific for SLEand indicates a poor prognosis
4- Anti - Scl. - 70
It is a marker for Scleroderma (20-50%).
5- Ab to Ro and La particles in SLE and Sjogren's syndrome.
6- Ab to centromere in CREST $
7- Anti-RNP (ribonucloprotien) in cases of mixed connective tissue disease and in SLE.