Anti Nuclear Antibody Test ( ANA; FANA )
The immune system synthesizes large amounts of proteins called antibodies. This synthesis is carried out by leukocytes, the body’s defense cells. These antibodies recognize and fight organisms that are harmful to the body under normal conditions. Sometimes these antibodies detect the body’s own molecules as foreign or harmful and fight these molecules. For this reason, they are called autoantibodies and as a result of this, autoimmune inflammatory diseases occur.
Anti Nuclear Antibody (ANA) are autoantibodies formed against various structures in the nucleus of the human cell. There are several methods for detecting ANA. One of these is a blood test known as Fluorescent Antinuclear Antibody. This test is also called FANA because of its method. In this method, fluorescently labeled antibodies are viewed under the microscope, and evaluation is made according to the pattern and density of these antibodies.
FANA test results are reported according to titrations and patterns generated by autoantibodies. Patterns are defined as homogeneous, mottled, centromere. The titrations of the blood sample are prepared by adding saline to the serum portion of the blood (1/40, 1/80, 1/160…).
When this test is considered in patients with appropriate clinical complaints;
It can be detected positively in the course of systemic diseases such as.
Positivity can be detected at low levels in healthy people without any disease. This situation can be seen between 3-15%. The development of these autoantibodies is age-related, and ANA positivity can be up to 10-37% in healthy individuals over 65 years of age. A negative ANA test indicates the absence of these autoantibodies in the body, while a positive ANA test alone does not indicate the presence of an autoimmune disease. Again, some viral infections, the use of certain drugs, and some cancers can cause positive ANA test results. Therefore, for a definitive diagnosis, the patient’s history, symptoms, physical examination, and other blood tests should be evaluated together.
ENA PANEL
Another test called ENA (extractable nuclear antigen) profile should be performed in patients with positive FANA. These proteins, which show antigen properties, are named so because they are extracted from the nucleus using saline. Using the ENA profile test, it is investigated against which antigen the positive ANA test occurs. Because each antigen suggests a different disease. ENA profile;
- Anti-RNP: Mix may be positive in 95-100% of those with Connective Tissue disease, sometimes in SLE and Scleroderma.
- Anti-SS-A (Ro): positive in 75% of patients with Sjögren’s Syndrome, and in some patients with SLE and Scleroderma
- Anti-SS-B (La): Positive in 60% of patients with Sjögren’s Syndrome, and in some patients with SLE and Scleroderma
- Anti-Sm (anti-Smith antibody): positive in 30% of SLE patients
- Scl-70(anti-topoisomerase antibody): Positive in 60% of patients with scleroderma
- Anti-Jo-1 Antibodies: Positive in 30% of patients with polymyositis
More than 100 antigens have been identified that cause the formation of ANAs. However, most of them are not used clinically. The ones that are used extensively clinically are the antigens that cause the development of the 6 antibodies mentioned above.
In the presence of symptoms and signs suggestive of autoimmune diseases other than the positive ANA test, the ENA panel can be investigated.
These symptoms and signs;
The ENA panel is important in detecting autoimmune diseases as well as in differential diagnosis to determine which type it is. The level of ENA autoantibodies may vary in measurements at different times. However, once these antibodies are formed, they remain in the person for life.