How can a blood test result for ANA be positive for 10 or more years and then become negative for the last year?

Are you being tested for Lupus? I don't see in my text (Labratory and Diagnostic Tests with Nursing Implications) that this is possible. You may need a repeat blood test.

AN ana [ anti nuclear antibody ] test is not specific. That is, there can be plenty of false positives.

The diagnosis of Lupus /sle is made on the basis of your history, if any , of particular symptoms, as well as on more specific lab tests [ such as anti double stranded dna antibodies ] .

The ANA or anti-nuclear antibody test can have varying results. A positive ANA can be caused by a number of things. Sometimes it is a clue that a person has lupus. There is no single definitive laboratory test that indicates lupus, rather if a patient meets 4 or the 11 symptoms set out by the American Coillege of Rheumatology and other conditions have been ruled out, then lupus is a real consideration.

I have lupus. If you tested me right now, I would probably have a negative ANA. Why? The disease is quiet at the moment.