ANA (Antinuclear Antibody)
Definition
The immune system produces proteins called antibodies to fight foreign substances such as viruses and bacteria. Antinuclear antibodies, however, mistakenly target healthy cells. Having some present is normal; high levels may point to an autoimmune condition.
Purpose
Helps diagnose autoimmune conditions: systemic lupus erythematosus (SLE), rheumatoid arthritis, scleroderma, Sjögren syndrome, Addison disease, autoimmune hepatitis, and thyroid disease. It is usually ordered for symptoms such as fever, rash, fatigue, joint pain, muscle pain, or abdominal discomfort.
Results
- Negative, no antinuclear antibodies detected; the likelihood of an autoimmune condition is lower but not completely ruled out
- Positive, antibodies were found. This may point to SLE, another autoimmune condition, a viral infection, or other conditions
Risks and Limitations
A positive ANA alone does not mean disease. Some healthy people have antinuclear antibodies, and levels rise with age; especially in women over 65, many healthy adults may test ANA positive.
Some medications can also cause a positive result without disease being present. The test alone cannot diagnose a specific condition; further testing is needed.