It's much more likely to have a false positive than a false negative test. Almost everyone who has lupus tests positive for the anti nuclear antibody test (ANA). That tests suggests someone might have lupus and prompts the doctor to do other tests to rule in/out lupus. If you're not positive for that test its very unlikely that you have lupus.

Lupus is diagnosed on the basis of the ANA test and a suite of symptoms plus other positive blood tests. Not everyone who has lupus will test positive for all these factors. A doctor will at all these factors to determine if someone has lupus.

You can find out more about lupus at

http://www.healthcentral.com/chronic-pain/guide-154531-75.html