If you've gotten a blood test for herpes, and it came up positive, the chances that you actually have herpes are lower than you think.
As STAT reports, the most commonly used herpes test is so often wrong that the US Preventive Services Task Force says that your doctor should not order it for you unless you already have symptoms of herpes. The same is true in Australia, with the government-run SA Health website noting:
All tests may sometimes give an incorrect result. The herpes blood test varies in its reliability, so the meaning of a test result must be considered along with your medical history.
That means that if you're just getting a bunch of tests run - say you want to know your HIV status - adding a herpes test to the order isn't helpful.
If you do get a positive result, make sure you talk it over with your doctor, and ask how likely the test is to be correct. Also ask what other information they are using to determine whether you do, in fact, have herpes.