This article talks about how common false positives are with herpes antibody tests. It's also why I don't ultimately put much stock in viral testing for MECFS...
The problem, said Christine Johnston, a physician and researcher at the lab, is “low-positive” results of antibodies to HSV-2. The cutoff for a positive result on the HerpeSelect test, manufactured by Quest Diagnostics, is 1.1. A 2005 studypublished in the journal BioMed Central Infectious Disease found that index values above 3.5 yielded over 90 percent accuracy — but scores between 1.1 and 3.5 had around a 50 percent chance of being wrong.
What’s more, scores falling just above the 1.1 cutoff had an almost 90 percent chance of being wrong.