Does a false positive elisa hiv test mean someone has a autoimmune disease? or could it be anything? do people find out why they get these results?

False (+) = error: Nothing can/should be interpreted from a false positive test, once verified as truly negative. There are a few specific exceptions to this, but in general, you should be tested for the diagnosis being considered.

No: While false positives can be from nothing specific, they can be related to infections from other viruses that may make similar antibodies that can react with elisas, but this has to be confirmed with western blot. I personally would ask for two confirmations as it can take up to six weeks for viral levels to be high enough to be sure with the test. Check with infectious disease doc to be safe.