The ANA test (antinuclear factor) is a test indicated to identify antibodies produced by the body that attack the body’s own cells and tissues, helping to diagnose autoimmune diseases such as systemic lupus erythematosus (SLE).
This exam is based on the search for abnormal antibodies and identification of their reaction pattern against cells, also called immunofluorescence pattern, which can be verified under a microscope.
In case of changes in the ANA exam, it is recommended to consult a rheumatologist. Although it is normal to have a low test result, when this number is high, it could mean an autoimmune disease and other tests may be indicated to confirm the diagnosis.
What is it for
This ANA exam can help diagnose autoimmune diseases such as:
- Lupuswhich is an autoimmune disease characterized by inflammation of the joints, skin, eyes and kidneys, for example;
- Dermatomiositewhich is an inflammatory disease characterized by muscle weakness and dermatological lesions;
- Juvenile idiopathic arthritisin which there is inflammation of one or more joints in children;
- Rheumatoid arthritis, in which there is pain, redness and swelling of the joints. See how to identify rheumatoid arthritis;
- Sclerodermawhich is an autoimmune disease characterized by increased collagen production, causing hardening of the skin and joints;
- Sjögren’s syndromewhich is characterized by the inflammation of various glands in the body, resulting in dry eyes and mouth, for example.
Generally, the doctor suspects these diseases when the person presents symptoms that take a long time to disappear, such as red spots on the skin, swelling and/or pain in the joints, excessive tiredness or recurring fever.
How to prepare for the FAN exam
No special preparation is necessary for the ANA exam, it is only recommended to inform the doctor about the medication being used and possible health problems.
How the exam is carried out
The ANA exam is carried out in specialized clinics or hospitals by collecting a small amount of blood, which is sent to the laboratory for analysis.
In the laboratory, the person’s blood is placed in contact with a special cell sample, and then a fluorescent dye is added to identify the antibodies and check their reaction pattern against the cells under the microscope.
What does the result mean
The result of the FAN exam may be:
- Negative or non-reactivewhen the result is 1/40, 1/80 or 1/160;
- Positive or reagentwhen the result is 1/320, 1/640 or 1/1280.
A negative result does not mean that there is no autoimmune disease. This way, even if the test is negative, and according to the symptoms presented, the doctor may order other tests to confirm the diagnosis.
When the ANA exam is positive, the positivity pattern is observed, which is based on the fluorescence seen under the microscope, which helps to better distinguish the type of disease, which may include:
- Homogeneous nuclear: is the most common pattern and can indicate diseases such as lupus, rheumatoid arthritis or juvenile idiopathic arthritis, depending on the antibody identified. If the presence of anti-DNA or anti-histone antibodies is identified, it is indicative of lupus;
- Centromeric: is normally indicative of scleroderma;
- Fine dotted nuclear: generally indicates Sjögren’s syndrome or lupus, depending on the antibody identified;
- Thick dotted nuclear: lupus, rheumatoid arthritis or systemic sclerosis according to the antibodies identified;
- Continuous nuclear membrane: may indicate autoimmune hepatitis or lupus;
- Punctate nucleolar: is usually a sign of systemic sclerosis.
These results should always be interpreted and evaluated by a doctor, and it is common for more tests to be carried out before confirming the diagnosis.
Bibliography
- UPTODATE. Patient education: Antinuclear antibodies (ANA) (Beyond the Basics). 2021. Available at: <https://www.uptodate.com/contents/antinuclear-antibodies-ana-beyond-the-basics>. Accessed on May 31, 2023
- MAYO CLINIC. ANA test. Available at: <https://www.mayoclinic.org/tests-procedures/ana-test/about/pac-20385204>. Accessed on May 31, 2023ICAP. ANA Test in Children. Available at: <https://anapatterns.org/nuclear_patterns.php>. Accessed on May 31, 2023
- STATPEARLS. Biochemistry, Antinuclear Antibodies (ANA). 2022. Available at: <https://www.ncbi.nlm.nih.gov/books/NBK537071/>. Accessed on May 31, 2023
- AMERICAN COLLEGE OF RHEUMATOLOGY. Antinuclear Antibodies (ANA). Available at: <https://rheumatology.org/patients/antinuclear-antibodies-ana>. Accessed on May 31, 2023
- HERMES PARDINI LABORATORY. Importance of the title in the interpretation of FAN HEp-2 results. 2012. Available at: <https://www3.hermespardini.com.br/repositorio/media/site/profissionais_da_saude/boletins_tecnicos/boletim_tecnico_fan_hepp2.pdf>. Accessed on October 25, 2019
- GROUP FLEURY. To avoid the pitfalls of idiopathic positive ANA syndrome. 2011. Available at: <http://www.amaissaude.com.br/medicos/boletim-medico/Documents/boletim_saibamais_junho2011.pdf>. Accessed on October 25, 2019
