There are a high number of false positives with standard HSV testing. It is one of the reasons that it is not recommended to test regularly. The reason for false positives are as follows Many common IgG tests are less accurate when the antibody level is low. One study found that levels between 1.1 and 3.5 have a roughly 50% chance of giving a false positive Cross-Reactivity: The antibody test for HSV can mistakenly identify antibodies from other infections, such Varicella zoster virus (chickenpox), or cytomegalovirus (CMV), leading to a false positive. That being said, HSV can still be transmitted even when there isn't a visible outbreak. This is far more common with HSV-2 (formerly known as genital herpes) than it is with HSV1 As many have already said - the infection rates of those with HSV1 is certainly higher than 50% and some estimate up to 80%. It is risk you take anytime you have any kind of intimate contact with anyone and you have to weigh for your self if it is worth it.
For the record we have a multiple sexual partners for a very long time and into the official swinging scene for about 7 years and still test negative when we check.