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The FAN exam (antinuclear factor) is the exam indicated to identify the presence of autoantibodies, which are antibodies produced by the body itself and that attack its own cells and tissues, being normally requested to assist in the diagnosis of autoimmune diseases, mainly Systemic Lupus Erythematosus (SLE).
This test is based on the fluorescence pattern of antibodies, being possible to visualize under a microscope and help in the diagnosis of several diseases besides lupus, such as Sjögren's syndrome, rheumatoid arthritis, dermatomyositis and scleroderma, for example.
Although it is normal to have a low ANA test result, when this number is very high, it can mean that there is an autoimmune disease, which needs to be identified and treated as soon as possible to relieve symptoms and prevent complications.
What is it for
This ANA test can help diagnose autoimmune diseases such as:
- Lupus, which is an autoimmune disease characterized by swelling of the joints, skin, eyes and kidneys, for example;
- Rheumatoid arthritis, where there is pain, redness, and swelling of the joints. See how to identify rheumatoid arthritis;
- Juvenile idiopathic arthritis, in which there is inflammation of one or more joints in children;
- Autoimmune hepatitis, where the presence of autoantibodies causes inflammation in the liver. Know the main symptoms of autoimmune hepatitis;
- Scleroderma, which is an autoimmune disease characterized by increased collagen production, causing the skin and joints to harden;
- Dermatomyositis, which is an inflammatory disease characterized by muscle weakness and skin lesions. Learn more about dermatomyositis;
- Sjögren's Syndrome, which is characterized by inflammation of various glands in the body, resulting in dry eyes and mouth, for example. Here's how to recognize the symptoms of Sjögren's Syndrome.
Generally, the doctor may be suspicious of these diseases if the person has symptoms that take a long time to disappear, such as red spots on the body, swelling, constant pain in the joints, excessive tiredness or mild fever, for example.
How the exam is done
This test is very simple, requiring only a small amount of blood to be taken by a trained professional, which is sent to the laboratory for analysis.
Blood collection is usually done in the hospital, but it can also be done in specialized clinics, both for adults and children. In the case of babies, the collection is usually done with a small prick on the foot, without the need to use the needle.
In the laboratory, the test is performed by adding a fluorescent dye marked with the antibodies to be identified in the sample. Then, the dye-labeled blood is placed in a container containing a human cell culture known as Hep-2 cells, which allows clear visualization of various cell structures and phases of the cell cycle. Thus it is possible to make the diagnosis, since it is made from the fluorescence pattern observed through the microscope.
What preparation is needed
There is no special preparation for the ANA exam, it is only recommended to inform the doctor about the medication being used and possible he alth problems.
What the results mean
In he althy people, the ANA test is usually negative or non-reactive, with values such as 1/40, 1/80 or 1/160. However, this does not mean that whenever it is negative, there is no autoimmune disease.In this way, even if it is negative, and according to the symptoms presented, the doctor may order other tests to confirm that it is not an autoimmune disease.
On the other hand, when the result is positive, or reagent, it usually presents values of 1/320, 1/640 or 1/1280. In addition, there is still the positivity pattern that is based on the fluorescence seen under the microscope, which helps to better distinguish the type of disease and which can include:
- Homogeneous nucleus: may indicate the presence of lupus, rheumatoid arthritis, or juvenile idiopathic arthritis, depending on the antibody identified. If the presence of anti-DNA, anti-chromatin and anti-histone antibodies is identified, it is indicative of lupus;
- Centromeric dotted nucleus: usually indicative of scleroderma;
- Fine speckled nucleus: usually indicates Sjögren's syndrome or lupus, depending on the antibody identified;
- Coarse stippled nucleus: lupus, rheumatoid arthritis or systemic sclerosis according to identified antibodies;
- Fine speckled cytoplasmic: may be polymyositis or dermatomyositis;
- Continuous nuclear membrane: may indicate autoimmune hepatitis or lupus;
- Spotted nucleus: usually a sign of systemic sclerosis.
These results should always be interpreted and evaluated by a physician and, in almost all cases, further tests are necessary before confirming the diagnosis.