Can an HIV test have a false positive result? How? In which circumstances?

Someone I know had a test done a month ago in London. He then moved to another country and had the test redone for employment purposes and now it show HIV positive. The test was repeated. Both positive. He is devastated as he has had no contact with an infected person.

Usually they do an ELISA test which has a high false positive rating but it is just used to see if they should even be suspicious. If it does turn out positive, whether false or not, they run another test, Western Blotting I think, where that is a better indication of positive or not. So its kinda hard to say that it is a false positive after those 2 tests are done.

You probably know already but it is spread by blood contact and sex.

Obviously he has had some form of contact ( not necessarily sexual ) with an infected person. Possibly with a needle stick.

Yes ELISA, the common HIV conventional test may give a false result--consequent on the incubation of the possible HIV virus and the spread...sometimes it doesnt detect HIV and sometimes it gets viruses mixed up and so gives a false result...Tell your friend to do Western Blot, it is more precise and accurate than ELISA. It may be positive, maybe there was an unknown form of infection, possibly an injection, even a simple manicure you never know...but hopefully he doesnt.

i think you are saying a false negative result. Your friend was initially negative then she turned out positive later on. Yes it could happen especially early on in the disease when no antibodies are present yet in the blood. i positive HIV test could take from 2 months to years before it can be detected in the blood actually.