A positive ANA (Anti-Nuclear Antigen) is unreliable UNLESS the ANA titer is markedly elevated e.g. 1:150, 1:200, 1:250. With regards to inflammatory markers such as ESR, ESR, D-Dimer, they are pretty much worthless except in TWO clinical scenarios which you all can ask Dr. Wikepedia or Dr. WebMD or another one of those quack sites. Back to the elevated ANA titer, you'd want to confirm the dx with other tests which have a very high specificity (i.e. very few false positive tests) for SLE such as anti-dsDNA (well done, Stewie) and anti-Sm antibodies. You could also r/o drug-induced SLE by testing for anti-histone antibodies but hey, lots of doctors are stupid.