How to Get a Western Blot Test for HSV-2?

Getting a Western blot test for HSV-2 requires more effort than a standard blood test because the Western blot is not available at most commercial laboratories or walk-in clinics. The test has long been considered the gold standard for confirming herpes simplex virus type 2 infection, with standard screening tests producing false-positive rates high enough to make confirmation genuinely important. Navigating the process involves understanding why the Western blot exists, who can order it, and what your results will actually tell you.

Why the Standard Blood Test Is Not Enough

Most clinics and commercial labs use enzyme-linked immunosorbent assay (ELISA) tests to screen for HSV-2 antibodies. The most widely used version in the United States is the HerpeSelect HSV-2 IgG ELISA. These tests look for antibodies to a protein called glycoprotein G-2, which is specific to HSV-2, and they return a numeric index value. An index above 1.1 is typically reported as positive.

The problem is that these tests produce a startling number of false positives, especially in populations where HSV-2 is not extremely common. A 2025 study comparing HerpeSelect and another ELISA (NovaLisa) against Western blot confirmation found that HerpeSelect had a positive predictive value of only about 26%, while NovaLisa was even lower at around 18%. Both ELISA tests dramatically overestimated HSV-2 prevalence: HerpeSelect flagged roughly 27% of samples as positive, and NovaLisa flagged about 34%, while the Western blot confirmed a true seropositivity rate of just 8.3%.¹ In practical terms, if you are in a lower-risk group and your ELISA comes back positive, the odds that it is a false positive can be disturbingly high.

This is the fundamental reason people seek a Western blot. It is not about getting a fancier version of the same test. It is about getting a genuinely different and more accurate answer, because the screening test’s accuracy in many real-world scenarios is poor enough to be misleading.

What the Western Blot Actually Does Differently

An ELISA test essentially asks one question: did the blood react to a single target protein? The Western blot separates the viral proteins and tests the blood sample against multiple HSV-specific antigens simultaneously. This means it can distinguish true antibody responses from cross-reactions with unrelated proteins or with HSV-1 antibodies, which are a common source of false positives on ELISA.² Type-specific serological tests that detect antibodies to glycoprotein G-1 (HSV-1) and glycoprotein G-2 (HSV-2) were a significant advance in herpes diagnostics, but the ELISA format still runs into trouble in borderline cases.³

The Western blot’s ability to evaluate antibody responses to a panel of viral proteins rather than a single target is what gives it its superior specificity. False positives on a Western blot are rare. When the Western blot says negative, you can be confident. When it says positive, the infection is almost certainly there.

Where to Get the Test and How to Order It

The most well-known HSV Western blot in the United States has been the one performed by the University of Washington (UW) Clinical Virology Laboratory in Seattle. For decades, this lab served as the primary reference laboratory for HSV Western blot testing in the country, accepting samples from clinicians nationwide. Data from this lab spanning 1999 through 2020 covered over 162,000 samples, with specimens arriving both from within the UW healthcare system and from outside sites across the country.⁴

However, the availability of this particular test has fluctuated. At times, the UW lab has limited or paused external orders, and current availability should be confirmed directly with the lab. If the UW test is not available to your clinician, a European-manufactured Western blot made by Euroimmun (marketed as EUROLINE-WB) is used in some clinical and research settings and has served as the reference standard in recent comparative studies.¹⁵

Regardless of which lab performs the test, you cannot order it yourself. A healthcare provider must submit the order. The general steps look like this:

• Get a clinician on board: You need a doctor, nurse practitioner, or other provider willing to order the test. Not all providers are familiar with the Western blot for HSV, so you may need to educate them or seek out a provider who specializes in sexual health or infectious disease.
• Have blood drawn: A standard blood draw is done at a lab or clinic. The serum is separated and shipped to the testing laboratory.
• Wait for results: Turnaround time has historically ranged from one to several weeks, depending on the lab and shipping logistics. This is not a rapid test.

Some sexual health clinics and STI-focused telehealth services are familiar with the process and can facilitate the order more smoothly than a general practitioner who has never heard of the test. Online patient communities often share updated information about which providers and services currently offer access.

When to Pursue a Western Blot

Not everyone who gets an HSV-2 blood test needs a Western blot. The scenarios where it adds the most value share a common thread: the initial result is ambiguous or the person’s risk profile makes a false positive plausible.

• Low-positive ELISA index values: ELISA results with an index between 1.1 and 3.5 are the most unreliable. Many clinicians and guidelines now recommend that any index value in this range be confirmed with a second test, ideally a Western blot. The higher the index value, the more likely the result is a true positive, but even values above 3.5 are not guaranteed to be correct in low-prevalence populations.
• No history of symptoms: If you have never had a recognized outbreak and your only evidence of infection is a positive ELISA, confirmation becomes especially valuable. Roughly 80% or more of people with HSV-2 have either mild or unrecognized symptoms, so a positive result in an asymptomatic person is not impossible. But in a low-prevalence group, the math of false positives means that a significant fraction of positive ELISAs in asymptomatic people are wrong.
• Discordant couple situations: If one partner tests positive and the other negative, confirmation has real consequences for how the couple manages risk, disclosure, and daily life. A false positive in this context can cause unnecessary relationship damage.
• Pregnancy planning: Accurate HSV-2 status matters for managing the risk of neonatal herpes transmission during delivery. A false-positive result could lead to unnecessary interventions, while a false-negative could leave real risk unaddressed.

If your ELISA index is very high (above 5.0 or so) and you have a clinical history consistent with herpes, the ELISA is probably correct and a Western blot is less likely to change the picture. But if there is any doubt, the Western blot resolves it more definitively than repeating the same ELISA.

Timing Matters More Than You Might Expect

One counterintuitive finding about HSV blood tests is that the Western blot actually takes longer to turn positive after a new infection than the ELISA does. A study tracking seroconversion after newly acquired HSV-2 found that the HerpeSelect ELISA detected antibodies at a median of about 21 to 23 days after symptom onset, while the Western blot took a median of 40 to 47 days.⁶

This means that if you rush to get a Western blot too early after a possible exposure, you could get a false negative simply because your body has not yet mounted a robust enough antibody response for the more demanding test to detect. The commonly cited window for reliable serological testing is at least 12 weeks after a potential exposure, though some experts suggest waiting even longer for the Western blot specifically. Testing too early is one of the most common mistakes people make when seeking confirmation.

If you had a visible sore or lesion at the time of a suspected exposure, direct testing of the lesion by PCR (polymerase chain reaction) or viral culture is far more useful than any blood test. Blood tests detect antibodies from past infection; swab tests detect the virus itself in an active lesion. The two serve different diagnostic purposes.

Understanding Your Western Blot Results

Western blot results come back as positive, negative, or indeterminate. The first two are straightforward. The third category is less commonly discussed but affects a meaningful number of people.

Across more than 162,000 samples tested at the UW reference lab over two decades, roughly 2.4% of results came back as indeterminate for HSV-2. Interestingly, the proportion of indeterminate results increased over time, rising by about 0.16 percentage points per year, while the proportion of positive results decreased. Indeterminate results were also more common among people who were HSV-1 seropositive, suggesting that existing HSV-1 antibodies can create borderline patterns even on the Western blot.⁴

If you get an indeterminate result, the usual recommendation is to retest after several weeks to see if the antibody pattern clarifies. An indeterminate result does not mean positive. It means the test could not confidently categorize the sample, and more time or a repeat test is needed. This is frustrating but genuinely better than a definitive but wrong answer.

Cost, Insurance, and Practical Barriers

The Western blot is not cheap relative to a standard ELISA, which typically costs between $20 and $100 at commercial labs. The Western blot has historically cost several hundred dollars, and insurance coverage is inconsistent. Some insurers cover it as a confirmatory test when a clinician documents the medical necessity (such as an equivocal ELISA result), while others classify it as a send-out test and decline coverage.

The biggest practical barriers are not financial, though. They are logistical and informational. Many primary care providers have never ordered the test and may not know it exists or how to arrange it. Patients often end up doing significant legwork themselves: researching the current ordering process, identifying a willing provider, and in some cases coordinating the blood draw and shipping logistics. Sexual health specialists, dermatologists with herpes experience, and infectious disease physicians are generally more familiar with the process.

The testing landscape has also shifted somewhat. Some newer immunoblot assays (which are closely related to Western blots but use slightly different formats) are becoming available through additional laboratories. These are not identical to the classic UW Western blot, but they serve a similar confirmatory purpose. Ask your provider about current options if the traditional Western blot route proves inaccessible.

The Emotional Weight of Getting Tested

It is worth acknowledging that the process of pursuing confirmatory testing for HSV-2 is not purely a laboratory exercise. Research on the psychological impact of herpes serological screening has identified a range of emotional and psychological responses to receiving a positive result, including distress, fear of disclosure to partners, feeling socially stigmatized, and concern about sexual desirability. Some of these responses were time-limited, fading as people adjusted, while others persisted.⁷

This is relevant to the Western blot question because people seeking confirmation are often already in an anxious state. They may have received a positive ELISA and are living in limbo, unsure whether they truly have the infection. The weeks of waiting for a Western blot result can intensify that anxiety. At the same time, many people who pursue the Western blot and receive a negative result describe enormous relief, because the confirmation resolved a diagnosis that turned out to be wrong.

The US Preventive Services Task Force does not recommend routine serological screening for genital herpes in asymptomatic adults, in part because of the psychological harms of false-positive results and in part because of the limitations of available screening tests.⁷ If you are already in the situation of having a positive ELISA, though, that recommendation is somewhat beside the point. The question is no longer whether to screen but whether to confirm.

What a Confirmed Positive Means for Daily Life

If the Western blot confirms that you do carry HSV-2, the practical next step is understanding what the infection looks like over time. One important finding that surprises many people is that viral shedding occurs even when no symptoms are present. A large study found that people with symptomatic HSV-2 shed the virus on about 20% of days sampled, while people with asymptomatic infection shed on about 10% of days. During subclinical shedding episodes, the amount of virus present was similar regardless of whether the person had a history of recognized symptoms.⁸

This means that even people who never experience noticeable outbreaks can transmit the virus to partners. It also means that the difference between “symptomatic” and “asymptomatic” HSV-2 is less binary than many people assume. Antiviral suppressive therapy with medications like valacyclovir reduces both outbreak frequency and the rate of shedding and transmission. Condoms further reduce transmission risk. Neither eliminates it entirely, but together they bring the annual transmission risk in discordant couples down substantially.

Understanding your status accurately, which is the whole point of pursuing a Western blot, allows you to make genuinely informed decisions about disclosure, suppressive therapy, and risk reduction. A false positive from an ELISA can lead to unnecessary medication, unnecessary disclosure of an infection you do not have, and unnecessary emotional burden. A false negative can leave you unaware of a real infection. The Western blot, despite its logistical hassles, gets closer to the truth than any other available blood test for HSV-2.

HSV-1 Versus HSV-2 on Serological Tests

One complication that comes up repeatedly in HSV testing is the interaction between HSV-1 and HSV-2 antibodies. Most adults have been exposed to HSV-1 (the virus historically associated with oral cold sores, though it increasingly causes genital infections too). Pre-existing HSV-1 antibodies can partially cross-react on HSV-2 ELISA tests, contributing to false positives. They can also blunt the HSV-2 antibody response in people who acquire HSV-2 later, potentially delaying seroconversion or producing borderline results.

The UW reference lab data showed that indeterminate HSV-2 Western blot results were significantly more common in people who were HSV-1 seropositive than in those who were HSV-1 seronegative.⁴ If you know you carry HSV-1, this is worth keeping in mind. Your HSV-2 serology, whether ELISA or Western blot, may be a little less clean to interpret than it would be for someone without prior HSV-1 exposure. The Western blot still outperforms the ELISA in this scenario, but the possibility of an indeterminate result is higher.

For people with HSV-1 who get an equivocal HSV-2 ELISA, the Western blot is arguably even more important, because the ELISA is more likely to be wrong in exactly this population. If the Western blot also comes back indeterminate, repeat testing after a few months is the standard path forward.