Positive Antinuclear Antibodies (ANA)
What does a positive ANA reading mean?
The ANA test identifies autoantibodies that target substances contained inside cells.
There are several methods used to test for ANAs which further complicates the interpretation and comparison of the values obtained.
The sensitivity and simplicity of an ANA test makes it extremely popular initial test to evaluate for lupus. Since more than 95% of individuals with lupus will test positive, a negative ANA test can be helpful in excluding that diagnosis.
However only 11 – 13% of persons with a positive ANA test have lupus and up to 15% of completely healthy people have a positive ANA test. Thus a positive ANA test does not automatically translate into a diagnosis of lupus or any autoimmune or connective tissue disease.
How should I handle a positive ANA reading?
Remember, a single positive ANA does not imply autoimmune disease, nor does a positive ANA require immediate treatment.
Lab levels vary; some autoantibodies are normal and this result may not indicate a problem.
A positive ANA reading alone does not indicate an autoimmune disease:
- The prevalence of ANAs in healthy individuals is about 3 – 15%.
- The production of these autoantibodies is strongly age-dependent, and increases to 10 – 37% in healthy persons over the age of 65.
- Even healthy people with viral infections can have a positive ANA, albeit for a short time
- Some medications can cause a positive ANA
- Other conditions, such as infections or cancer, can cause a positive ANA
To make a definite diagnosis, one should undertake a comprehensive history, paying particular attention to any constitutional/systemic, mucocutaneous or musculoskeletal symptoms.