HSV 2 IgG Screening Index

Many people with HSV-2 have never recognized an outbreak. Type-specific IgG testing looks for antibodies produced after infection, which usually persist indefinitely. A confirmed positive generally indicates a lasting infection, but an initial positive screen can be wrong. This distinction matters when the result could change a diagnosis or a conversation with your partner. CDC guidance

Type-specific antibody testing has an established role in selected diagnostic situations. Its numerical index has no established role as a measure of outbreak severity, contagiousness, or response to treatment. The useful question is whether the evidence supports infection, taking the assay, exposure history, symptoms, and timing into account. Laboratory interpretation

What the Number Measures

IgG is a class of antibody that can remain detectable long after an infection begins. Many type-specific HSV-2 assays look for antibodies to the viral surface protein glycoprotein G2. The index expresses the strength of the sample's reaction relative to the assay's calibration. It isn't a standardized antibody concentration, and different manufacturers' numbers aren't interchangeable. The studies discussed here used serum samples and several different assays, so their accuracy estimates describe those methods and study groups. Comparison of automated assays

The index cannot reliably establish when you acquired HSV-2. In a study of the HerpeSelect assay, values overlapped between recent and established infections, and some people with longstanding infection had persistently weak reactions. A low number doesn't establish that an infection is recent or fading. Study of index values

Why a Positive Screen Can Need Confirmation

False-positive results are especially concerning when the screening reaction is weak or the chance of infection was low before testing. The FDA has warned that HSV-2 antibody tests can produce false-reactive results and recommends confirmation when indicated. A screening label alone may not provide enough evidence for a diagnosis. FDA safety communication

A stronger screening reaction usually makes true infection more likely, but it doesn't guarantee it. Research comparing screening indices with an inhibition assay found false-positive and indeterminate results among strongly reactive samples too. An unexpected result still deserves attention even when its index looks convincing. Study of screening and inhibition results

Why Your History Changes the Interpretation

The chance that a positive result represents infection depends partly on how likely infection was before testing. In a study of women with genital ulcers, many weakly positive HerpeSelect results had supporting evidence from another antibody assay or direct viral detection. That finding doesn't make every weak positive in someone with sores a true infection. Genital sores have several possible causes. Study in women with genital ulcers

Accuracy also varies across populations. A systematic review of serum studies from sub-Saharan Africa found substantial differences between commercial HSV-2 antibody assays, including differences associated with HIV status. This is another reason to avoid applying a percentage from one study to every laboratory or person. Systematic review

False Negatives and the Window Period

Antibodies take time to become detectable. In one study, the subgroup with newly acquired HSV-2 and no previous HSV-1 antibodies reached a positive HerpeSelect result a median of 21 days after symptoms began, compared with 40 days for Western blot. Those are midpoints in a particular study, not deadlines by which everyone will test positive. The timing also depended on the assay and previous HSV-1 infection. Seroconversion study

Established infection can also be missed. In a small Dutch study of 33 people with recurrent genital HSV-2 confirmed by viral DNA testing, individual commercial antibody assays missed about 15% to 30% of infections. These were selected clinic cases, so the figures aren't a general false-negative rate for everyone taking this test. They do show why a negative antibody result cannot rule out herpes when a lesion test has already established the infection. Study of false-negative antibody results

Infection Without Recognized Outbreaks

Both HSV-1 and HSV-2 can cause genital herpes. HSV-2 is especially associated with recurrent genital disease. In pooled European studies using direct viral detection, HSV-2 accounted for about two-thirds of genital herpes cases, but a much smaller share of genital ulcers from all causes. Those findings describe the causes of lesions; an antibody index cannot identify the cause of a particular sore. European epidemiology review

People who haven't recognized outbreaks can still release HSV-2 from genital skin. Studies using repeated genital swabs found this less often in people without recognized symptoms than in those with symptomatic infection, but it occurred in both groups. Your antibody index doesn't show whether virus is present on your skin on a particular day. Genital shedding study

The Connection With HIV

HSV-2 infection is associated with a greater chance of acquiring HIV if you're exposed to HIV. A 2017 meta-analysis of 57 studies following people over time found about 1.7 times the risk with existing HSV-2 infection and about 4.7 times the risk with newly acquired HSV-2 infection. The association was stronger in general populations than in higher-risk groups. This association concerns HSV-2 infection status. It doesn't make a higher screening index a measure of HIV risk, and it doesn't establish that HSV-2 screening or lowering antibodies prevents HIV. Longitudinal-study meta-analysis30405-X)

When Results Can Be Misleading

• Recent infection: antibodies may still be developing when the sample is collected. A negative result during this period can miss infection. Seroconversion study
• HSV-1 antibodies: these can complicate interpretation on some platforms. A large study of HSV-2 inhibition testing linked stronger HSV-1 antibody reactions to indeterminate confirmation results, but didn't find the same association with negative confirmation results. Inhibition-assay study
• Pregnancy: an older study using specific glycoprotein-based assays found declining antibody levels and occasional temporary negative results during pregnancy. This doesn't establish that every current assay behaves the same way. Pregnancy study
• A different laboratory or assay: changes in the numerical index can reflect differences in calibration or test performance. Even results from the same platform aren't a validated way to monitor outbreaks or contagiousness. Assay comparison, index-value study

Why a Changing Index Doesn't Show Recovery

A result can change from positive to negative because the earlier result was false, because a true antibody response fluctuates, or because the tests differ. In a study following women over time, the rare HSV-2 positive-to-negative changes were traced to false-positive screening results. A separate study documented temporary negative results after confirmed new HSV-2 infection. A disappearing positive therefore needs interpretation; it doesn't prove that an infection cleared or that the original result was wrong. Longitudinal reliability study, study of newly acquired infection

Where Screening Has Value

Testing can help when you have recurring genital symptoms without a confirmed diagnosis, or when a partner has genital herpes. The case for routinely screening everyone without symptoms is different: false positives are common enough to cause harm, and studies haven't established that population screening improves health outcomes. The US Preventive Services Task Force recommends against routine screening in people without symptoms, including during pregnancy. That recommendation leaves room for testing prompted by symptoms or a specific exposure. CDC testing information, USPSTF recommendation