Genital Herpes Blood Testing: Is it Really that Accurate?

Most sexually active adults are aware that they should have safe sex as well as routine STD and HIV testing in order to protect the health of themselves and their partners. However, with some STDs the means of testing is little known and even in the medical community still very much developing. Asides from HIV (which is much less prevalent in the United States) probably the worst and most feared STD is genital herpes. Until recently I did not know that there was anyway to test for the virus outside of a visual inspection if, and when, sores appeared. Upon routine testing I learned that there is now a blood test that can detect HSV-2 antibodies. This is when I learned the complexity and issues of this form of testing.

Until very recently there were two types of testing that were relied upon. These two types are IGG and IGM testing. IGM is suppose to show any present and new infection while the IGG shows past infection and subsequent building up of antibodies by the immune system. While most doctors, including a very popular blood testing lab called LabCorp. may now know or care to share this, IGM testing has shown to be ineffective and unreliable when it comes to detecting HSV-1 and HSV-2 infections and is generally not recommended by the leading Infectious Disease experts. Therefore, the reliable testing of IGG antibodies may take as long as 3 months to show positive on a blood test although most people with a new HSV infection will have developed a positive test by 6 weeks. Even with the presence of a lesion unless a culture is taken and tested by a doctor during the first sign of a sore these tests are highly unreliable. They have a re of about 50% false negatives because of this.

Even taking all this into consideration there continue to be more discrepancies when it comes to testing specifically without the presence of physical symptoms. (Although as we know the overwhelming majority of people with the virus never show physical symptoms and are unaware of the infection). The most widely offered and most commercially accurate test available to the public is a tested called the HerpesSelect ELISA test which is created by Focus Technologies located in California. This test is the most sensitive to newer infections and differentiates HSV-1 and HSV-2 infections. While HSV-2 is less rare nearly 70% of people have been exposed to HSV-1 infection which results in mouth sores and thus this distinction is needed. It is noted by focus technologies however that up to 30% of HSV-1 infections do manifest themselves genitally (although 70-90% of primary genital herpes infection are caused by HSV-2).

Focus Technologies claims that their test is 96%-100% accurate although these statistics seems to be fairly inaccurate. Anything that comes back under .90 is considered a negative result, while anything over 1.1 is positive. Anything between these two values is considered Equivocal and requires retesting. Anything over 3.5 is considered definitively HSV positive. Now, this is where the margin for error comes into place. Anything over 1.1 but less than 3.5 is in fact considered positive; however this is a low positive and while it may show an early infection, in the lake of any known physical symptoms this is when the reliability of the test is challenged. The first issue is that when HSV-1 is present the test tends to be less accurate when it comes to specificity. A study conducted in April 2005 and submitted to the American Sexually Transmitted Diseases Association stated:

"Based on findings from the PPV study, beginning in October 2002, our clinic began defining HSV-2 ELISA results as indeterminate if the HSV-2 index value was >1.1 to 2.9 in a person with antibody to HSV-1 by ELISA. "

Additionally this same study also found:

"Among men testing positive for HSV-2 as part of routine clinical care in our STD clinic, a group with a 13% prevalence of HSV-2 by ELISA, only 84% had a positive confirmatory HSV-2 Western blot. This estimate of the test's PPV is similar to a PPV of 81% for the clinical diagnosis of first-episode genital herpes reported in a previous study"

After the previous level at which one may be determined to be HSV-2 positive was challenged another study was conducted in Sub-Saharan Africa where HIV and HSV rates tend to be much higher than average and it was determined that due to the fact the some of these "low-positive" patients may indeed have HSV the cut off rate could not be raised to 3.5. With this being said, the article printed in April 2008 by the American Society for Microbiology showed:

"Serum samples from 346 (80%) women were found to be HSV-2 seropositive by HerpeSelect (index values of >1.1), of which 66 (19%) had low-positive index values (≤3.5). Samples from another six women were found to be equivocal (index values of 0.9 to 1.1), with one being associated with positive detection of HSV-2 DNA (in the lesional sample). Overall, 58% (36/62 patients) of women with low-positive HerpeSelect index values and 60% (164/275 patients) of women with high-positive HerpeSelect index values had molecular evidence of genital HSV-2 infection (P = 0.8)."

If 42% of these low positive individuals in an area where HSV is rampant, imagine the number in less infected regions? Even with two different types of blood tests and the lesional sampling only 71% of these were TRUE infections. While that number is still very high and thus was the justification for keeping the positive result to 1.1, but I can only imagine how many people have been told my a lab they are positive for herpes when in fact they are not.

Oddly enough there is a blood test called the Western Blot which is considered among the professionals to be considered the "gold standard" of testing. However there is only one lab in the United States that processes these blood samples, at the University of Washington Virology Lab, and results take a week or more for results. It is not FDA approved and is considered research thus your insurance company may not pay for it when it is the most costly test and if you are simply seeing your primary care physician or an OB-GYN they may not even be aware of its presence. This test is considered 99% accurate although it takes a bit longer than 6 weeks to reach this level of accuracy. Generally it takes 12 to 16 weeks after exposure to detect the antibodies.

These tests may provide the best results we have to date in testing for HSV-2, but a disease with such serious social and personal mental and physical ailments (as well as possible effects to an unborn child) should call for more accurate testing methods. I am sure in the future, eventually, the western blot will become the standard method of detection, but individuals that are incorrectly diagnosed as having genital herpes should have the availability and access to the real accuracy of these tests without having to scour through medical journals and internet postings.