Thank you for your question.
The threshold levels may vary slightly from one labe to another, but generally a value <0.9 is considered negstive, a value >1.1 is considered positive, and value between 0.9 - 1.1 is equivocal. An equivocal is not positive, but there is the possibility that there was a recent exposure that is on the increase and that a recheck will be positive. If repeat values are consistently equivocal, it is considered to be negative.
The usual IgG antibody response to an infection is an steady increase after initial exposure, but then a gradual lowering if there is no recurrent exposure. The first antibodies that are made arer IgM and the IgG are a reflection of long-term immunity. Once the immune system is primed, a second exposure will generate a rapid IgG antibody response. Since herpes infections tend to be recurrent, the antibody response will be maintained, but there is no specific number that would indicate whether it is a more recent or distant infection.
Therefore, the HSV2 level is positive, but the HSV1 is equivocal and should be rechecked.
The IgM test is accurate in that if it is elevated it reflects an infection, but it is not accurate to differentiate HSV1 & HSV2, which is why it is reported as a combined result. IgM also can be elevated in response to a recurrence and a negative test does not accurately reflect that there is no recent infection. IgG is the better test to differentiate HSV1 & HSV2 and will consistently be positive after exposure. The antibodies can be present within a few weeks, but may take 3-4 months. A negative result 4 months after a known exposure can be reliably stated to indicate that the person did not get infected from that exposure.
So basically there is no way to tell if it is recent or old??
Could the doctor be right with the time frame or is he just attempting to make a guesstimate?
There is no way to tell if it is recent or old based on the blood tests. If the equivocal result becomes positive, you can say that there has been a recent HSV1 infection.