hi bec

i've not had any issues with this one (pretty sure i haven't been tested!) - but doing a quick google search, i found this

Antinuclear Antibody Test (ANA) -- This test identifies certain autoantibodies typically present in the blood of people with lupus. Most people with lupus test positive for ANA. However, a positive ANA result can occur due to infections and other rheumatic or immune diseases. In addition, healthy people without lupus also can test positive.
is it possible you've tested positive and your doc is doing follow up tests to check whether there is a possibility of lupus (which is really difficult to diagnose) or whether you had the antibiodies due to other factors - if the first two tests were inconsistent results, they may be testing a third time to check the result again... perhaps their monitoring your immune responses... i'm just guessing, but it's something to consider - i doubt they'd be testing specifically for lupus, more to look at your immune antibodies in general...

if you're concerned, i'd ask your doctor directly why they're testing you again for this - can't hurt to ask! goodluck hun!