- ANA stands for "Antinuclear antibodies".
- Antibodies are proteins produced by white blood cells, which normally circulate in the blood to defend against foreign invaders, such as bacteria, viruses, and toxins.
- The antibodies that target “normal” proteins within the nucleus of a cell are called antinuclear antibodies (ANA).
- Most people have antinuclear antibodies, but typically in small amounts. The presence of large amount of autoantibodies or ANAs can indicate an autoimmune disease.
- A negative ANA reading means no antinuclear antibodies are present in the body.
- A positive ANA reading alone does not indicate an autoimmune disease.
The ANA titer is a measure of the amount of ANA in the blood; the higher the titer, the more autoantibodies are present in the sample.
Patient samples are often screened for antinuclear antibodies after being diluted 1:40 and 1:160 in a buffered solution. If staining is observed at both the 1:40 and 1:160 dilutions, then the laboratory continues to dilute the sample until staining can no longer be seen under the microscope. The level to which a patient's sample can be diluted and still produce recognizable staining is known as the ANA "titer."
Here is an example:
1:160 positive (titer reported as 1:160)
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