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Contents

Part 1

Part 1

Practical things to know

Part 2

Part 2

Herpes tests and what they check for

Part 3

Part 3

Before, during and after the test

Part 4

Part 4

Details of herpes tests

Part 5

Part 5

Choosing the right test

Part 6

Part 6

Tests accuracy and stats

Part 7

Part 7

Test interpretation

Part 1

PART 1

Practical aspects of genital herpes testing —
is herpes testing routine and necessary?

This is an important practical aspect of herpes testing you need to know about and understand before choosing to be tested for herpes.

Is herpes simplex virus antibody blood test necessary and routinely done?

Herpes testing is not a routinely performed test—it’s not a part of routine STD (sexually transmitted disease) tests ordered by physicians. Moreover, this test might not be done when someone asks for a “full” or “complete” STD panel.

Here is why herpes is not routinely tested for:

  • Early diagnosis will not change the disease prognosis.
    Usually, screening tests are recommended when there is a high chance of a better outcome if a condition is diagnosed earlier. This is not the case with herpes. Herpes is a lifelong infection, and there is no change in treatment strategy or prognosis if someone is diagnosed early.
  • Testing will not change sexual behavior.
    According to the CDC (Center of disease control and prevention), there is no proof of a herpes-positive person changing their sexual behavior (switching to pro nce) after learning about their herpes status. [1] Genital Herpes Screening FAQ https://www.cdc.gov/std/herpes/screening.htm
  • Testing will decrease quality of life.
    About 90% of people are herpes positive, and the majority of them—up to 80% of them—are unaware of that fact. They are asymptomatic and have no psychological or physical issues. However, once an asymptomatic person gets a positive result, they may start to feel stigmatized and ashamed, which will significantly lower their quality of life.
  • Testing will not reduce the chance of HIV acquisition.
    Though herpes increases the chance of HIV acquisition, early herpes diagnosis and treatment will not help to lower this risk.
  • There is a chance of a false-positive result is high.
    There is always a chance (up to 20%) of having false-positive test results (that is, the test indicates the presence of infection, but a person does not have it). This may lead to unnecessary financial and psychological issues.

Who should consider getting tested for herpes?

According to the CDC[2] Centers for Disease Control and Prevention (CDC). Genital Herpes - CDC Fact Sheet. https://www.cdc.gov/std/herpes/stdfact-herpes.htm , you should have herpes testing if:

✓ You have herpes-related symptoms (for example, genital itching and pain) and signs (fluid-filled blisters and sores) in order to exclude other conditions,

✓ You have had sexual intercourse with someone who is herpes-positive,

✓ You are pregnant and have a herpes-positive partner, or

✓ You have multiple sex partners and they want to undergo a complete STI screening.

Is it important to know the difference between the two herpes types, HSV-1 and HSV-2?

No, it is not important for a practicing physician. Here’s why:

There are some differences between the two herpes types (for example, HSV-2 has more frequent outbreaks and is more easily transmittable than HSV-1, especially during the first three month after exposure). But in clinical medicine, it’s important to know information if it somehow changes the treatment strategy or something else that’s important. But in the case of herpes, the treatment plan and prognosis is the same for both types.

Regardless of the herpes type:

  • People have a great long-term outcome (or at least the same outcome, regardless of which type they have). Unless a herpes-positive person has immunosuppression (people with HIV, people receiving chemotherapy, etc.), they won’t have any herpes-related life-threatening health complications. This is true for both herpes types (they have similar manifestation and prognosis).
  • The treatment and prevention are the same. The treatment for recurrent herpes is based on the anatomic location of the virus in the body, not the type of herpes causing it. As we know, both herpes types may affect both the oral and genital anatomic regions.

Herpes stigma

Although we know that both herpes types may be transmitted orally and genitally and may affect even virgins and those with only one sexual partner, some people may feel stigmatized when they learn they have HSV-2 because it’s is considered an sexually transmitted infection and known as “genital” herpes.

Part 2

PART 2

What do the different herpes tests measure?

Several herpes simplex virus tests exist. They’re designed to detect the presence of the herpes virus in different ways. [3] Herpes Tests https://patient.uwhealth.org/healthwise/article/en-us/hw264763#hw264782

Viral culture: This test is done using a swab of the herpes sore. The collected specimen is observed in a laboratory to see if the virus multiplies and grows.

This is done to confirm a herpes diagnosis (the initial diagnosis is made clinically; that is, based on visual examination). This test can distinguish between herpes 1 and 2. It is most accurate during the early stage of the outbreak when the sore has just formed.

Polymerase chain reaction (PCR) test: This test looks for DNA of the herpes virus and distinguishes between the two common herpes virus types, HSV-1 and HSV-2.

The test is done using venous blood, a specimen collectedby swabbing the sore, or cerebrospinal fluid collected via a spinal tap.

Tzanck smear: A sample for this test is collected by scraping the herpes sore. A healthcare professional puts it under a microscope to look for cells specific to a herpes infection.

Antibody test: This blood test looks for the herpes antibody (protein) produced for the herpes antigen. Every antibody type is uniquely produced for a specific antigen, so the test can differentiate between the herpes 1 and herpes 2 viruses. The antibody test is done using a blood sample and is the most commonly performed test.

Since this test detects the production of antibodies, which can take up to three months, it can give false negative results if it is done too early.

Part 3

PART 3

Having a herpes test: before, during, and after

Herpes simplex virus testing can be done different ways—as a blood test, swab test, or lumbar puncture—depending on the symptoms.

✓ If herpes symptoms are present, the doctor can swab the herpes blister or sore to collect fluid that can be cultured in the laboratory or examined using a PCR test.

✓ If there is no visible outbreak, a blood test can be performed to look for antibodies.

✓ If the doctor suspects a herpes brain infection (encephalitis or meningitis) due to HSV virus, a lumbar puncture test needs to be done.

Before the test

No special preparation is required for a blood or swab test.

During the test

✓ A specimen is collected for a swab test by rubbing a sterile swab against the sore or sometimes by popping a blister or scrabing its base with a scalpel.

✓ For a herpes blood test, a small sample of blood is taken from the vein using a small needle.

✓ A spinal tap (also called a lumbar puncture) [4] HSV DNA https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=hsv_dna_csf is usually done in a hospital setting. A provider collects spinal fluid with a needle inserted between two vertebrae at the lower part of the spine (the lumbar, or low-back, area). This is not a common procedure for herpes testing.

After the test

There are no post-test restrictions with blood and swab tests.
A swab test might cause slight temporary discomfort afterward.
A blood test might cause minimal soreness and bruising that is typically short-lived.
After a spinal tap, the patient must lie on their back for an hour or two.

Part 4

PART 4

Important details for different types of herpes tests

Here we will give details about some different types of herpes tests: the blood test (IgG, IgM, and Western blot) and the swab test.

What is the most commonly performed herpes simplex test and why?

The IgG test [5] Herpes Simplex Virus (HSV) Type 1-Specific Antibodies, IgG https://www.labcorp.com/tests/164897/herpes-simplex-virus-hsv-type-1-specific-antibodies-igg is also known as the herpes select test is the most commonly performed herpes blood test. It detects IgG antibodies for the two herpes types: HSV-1 and HSV-2.

IgG antibodies are proteins made by the immune system that develop in response to infection. IgG tests can differentiate between the two herpes types.

Here are a few reasons for the IgG herpes test’s popularity:

1. All doctors’ offices can do it

IgG tests are widely available since it is the easiest test to perform. It is a simple blood test and is performed at various health clinics, diagnostic centers, and hospitals.

2. There are fewer restrictions on its use

IgG antibodies last for a lifetime. Therefore, a person may get tested at any time to find out if they have herpes. The only time restriction is that two weeks should pass after exposure if the test is being done to find out if the patient has recently contracted the virus.

The IgG test may be performed on asymptomatic people, unlike swab (culture) tests, which should be performed within 48 hours after the appearance of herpes-specific blisters and is most accurate if it is performed within the first 24 hours.

3. Its accuracy is acceptable

The IgG test is about 94% accurate in detecting the infection. About 19% of the time, its results are false positive (that is, the test is positive for herpes infection when the person does not have herpes).

By contrast, the herpes IgM antibodies tests give almost 50% false-negative results. For that reason, the IgM antibodies test is not done for herpes screening at any stage.

Washington University herpes test: how it is different

The Washington University HSV test [6] HSV resources https://depts.washington.edu/herpes/pages/hsv_resources is considered the “gold standard” herpes blood test because it has:

  • Better accuracy
  • o Less chance of false-positive and false-negative results

It detects type specific herpes antibodies. The term “gold standard” means that other IgG herpes tests that are commercially available are compared to this test to assess their accuracy.

This test is exclusively performed at the University of Washington Virology Department, which makes this test less available to the general public.

In this infographics below, we summarize and compare the main practical parameters of the Washington University HSV test and the commercially available, commonly used Herpes Select® IgG antibodies tests.

Please note that the Washington University test may take a month or longer to get done and usually is not covered by health insurance.

To learn more, you can call 206-520-4600 and ask for an “HSV Type-Specific Serology information packet.”

We do not offer any assistance with Washington University herpes test in our office.

Illustration by STDcenterNY
Illustration by STDcenterNY

Herpes viral culture (swab) test: how it is different from
blood tests, how accurate it is, and its limitations.

First, I will mention a few test features that make this test desirable to doctors and then will mention important limitations.

It detects the actual virus.

Unlike blood tests that check your body’s response to the virus, the HSV culture (swab) test detects the presence of the actual herpes virus in the sample (fluid and skin) taken directly from a herpes-specific lesion.

It’s the only test that can tell if the current lesion is a herpes lesion.

This is the only test that can tell you that the skin lesion you see is a herpes lesion, as opposed to something else. By comparison, from all herpes blood tests and a doctor’s physical exam, one can only assume that skin lesions are a herpes outbreak.

It is very accurate.

The swab test(PCR test) is a very accurate test: if your results are positive, you can be 100% sure that you have herpes.

Swab test limitations: timing and technique

Timing

Unlike blood tests, which can be done at any point to confirm one’s herpes status—the swab test can be performed only during an outbreak. Moreover, it should be done within the first 48 hours (ideally 24 hours) of seeing blisters and sores.

Technique

Ideally the herpes blister that is swabbed should be broken by the doctor so concentrated fluid is collected for the testing. Dry sores cannot be swabbed.
In the table below, we compare the blood test (IgG) to a herpes swab (culture test).
Please note that the swab test can be performed by only a few specialized places that have the necessary viral collection kit.

Illustration by STDcenterNY
Illustration by STDcenterNY

IgM herpes test

IgM antibodies are proteins the body produces after contracting herpes. They become detectable 10 to 21 days after being infected (around the same time that IgG antibodies become detectable).

Unlike IgG antibodies, which persist for life, IgM antibodies might persist for a few months and then disappear. Occasionally, IgM antibodies can be detected even with recurrent infection.

Also unlike the IgG test, which looks for antibodies specific to the type of herpes, IgM testing does not differentiate between HSV-1 and HSV-2.

The CDC and other testing authorities discourage using a IgM test since it does not add any value in diagnosing herpes. [7] Discontinuation of Herpes Simplex Virus (HSV) IgM Testing https://news.mayocliniclabs.com/2019/11/11/discontinuation-of-herpes-simplex-virus-igm-testing/

Part 5

PART 5

Choosing the right genital herpes test

To choose the right test for you, you need to answer two questions:

✓ Do you have symptoms currently?

✓ If you don’t have symptoms, how much time has passed since exposure?

If symptoms are present

If you have symptoms, you can get a culture test, which is the most accurate test for determining whether skin lesions are a herpes outbreak. (The symptom that we are talking about here is a skin blister or sore, not skin redness or other systemic symptoms (fever, tingling, fatigue, etc.).

The culture test has a few limitations:

  • You should have a visible sore. Ideally the test should be performed within 24 hours of the blisters’ appearance (it is OK to do it within 48 hours).
  • Ideally the herpes blister should be intact and broken by a healthcare provider at the time of the test.
  • The sore should be wet. Dry, crusted sores cannot be swabbed.

If no symptoms are present

✓ You can get herpes IgG antibodies testing if at least three weeks have passed since exposure (ideally, three months).

✓ The swab test cannot be done if there are no symptoms.

Illustration by STDcenterNY
Illustration by STDcenterNY
Part 6

PART 6

Herpes tests accuracy

How accurate are the different genital herpes tests?

All available herpes tests are quite accurate when they’re done at the right time.

The right time is different for different herpes tests:
For swab or culture tests, the “right time” means getting it done while during an outbreak.
For both blood tests—IgG and the Western blot test offered by Washington University—the “right time” means long enough after exposure to be accurate.

Here are more details:

The culture test

✓ Should only be performed during outbreaks (when visible fluid-filled blisters are present)

✓ Is most accurate when performed within 24 hours after the appearance of herpes-specific blister(s) and when the blister(s) are fluid-filled (if it is crusted the doctor will not be able to collect enough fluid for testing)

✓ Is more reliable during the first outbreak.

✓ Is accurate if a sufficient amount of sample is collected (fluid with a high concentration of herpes virus)

The IgG test (Herpes Select and Washington University western blot)

If you have been exposed and are being tested for that particular exposure

  • The earliest it can be done is three weeks after the potential exposure (50% accuracy at that time)
  • The ideal time is 12 weeks after the potential exposure (92% of positive people will get positive test results)

If you want to know your status without reference a particular exposure

  • It can be done anytime.

What are the chances of false-negative results for the different herpes tests?

As with all available medical tests, herpes tests can give you false-negative results [8] Study questions reliability of diagnostic tests for herpes https://newsroom.uw.edu/news/study-questions-reliability-diagnostic-tests-herpes . The question is how often and when.

The definition of a “false negative” test is a test showing negative results when in reality you are positive for the disease. It means the test performed was not sensitive enough, for one reason or another, to pick up the infection.

It does not mean that the test is not accurate, but it should be done when certain conditions are met. Sometimes doctors do the test to see if it will come back positive; if the result is negative but they still think the patient probably has herpes, they know the test was not done under ideal conditions.

Below we discuss the chances of false-negative results for the different herpes tests.

The IgG test (Herpes Select and Washington University western blot)

The chance of a false-negative result with a herpes culture test

A herpes culture test’s likelihood of giving a false-negative result may reach 70%, roughly. However, the probability cannot be precisely determined because it depends on various factors, such as the following:

Timing after the appearance of blister(s)
Peak test accuracy is 24 hours after the appearance of herpes lesions.

Number and size of herpes lesions
If there are just a few small lesions, it will be hard to collect the needed amount of sample.

First versus subsequent outbreak
The chance of getting false-negative culture test results increases with every subsequent outbreak. Here’s why:

  • less concentration of herpes virus in the fluid
  • less severe outbreak with less blisters/sores available for fluid collections

The chance of a false-negative results with a herpes blood test
Herpes Select IgG test

  • The commercially available herpes IgG test has up to a 38% probability of false-negative results.
  • Usually, it’s because not enough time has passed after exposure (at least three weeks; ideally, three months).

Washington University HSV test

  • It is considered the gold standard blood herpes test.
  • exposure (at least three weeks, but full accuracy is reached three months after exposure).

What are the chances of false-positive results for the different herpes tests?

False-positive tests [9] Serological Screening for Genital Herpes: An Evidence Review for the U.S. Preventive Services Task Force [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK409115/ are less common than false-negative tests. But false-positive results can have a big psychological impact on some people who believe they have a condition that is not curable when in fact they don’t have it.

False-positive results may be due to an overly sensitive and not specific enough test that picks up a condition that can cross-react.

Here are the most practical and important details for each test:

✓ The herpes culture test (swab test) has a 0% chance of a false-positive test result. This means that a person who tests positive can be 100% sure that they have the herpes infection.

✓ The commercially available herpes IgG test (Herpes Select) has up to a 19% probability of revealing false-positive test results. This mostly happens with a low positive number (less than 4).

✓ The Washington University HSV test is considered the gold standard blood test, and the probability of getting a false-positive result is close to zero.

Part 7

PART 7

Interpretation of herpes tests

Once a herpes simplex virus test result is back, it’s time to interpret it. As with any herpes issue, it’s not straightforward.

HSV results will be given as negative (normal) or positive (also called abnormal).

The interpretation of the test depends on the type of test conducted.

Swab test (viral culture or PCR)

A positive /abnormal test means you may be 100% sure that you are herpes positive and that your current skin lesion is herpes.

A negative/normal test means one of two things:

✓ The skin that was swabbed is not a herpes lesion. Keep in mind that this does not mean you do not have latent herpes. (Being positive for herpes in the blood and having a herpes skin outbreak are two different things.)

✓ Not enough sample was collected—25% of herpes swab tests are considered false negatives.

Antibody blood test

A positive/abnormal test means you are most likely herpes positive.
But there is a 19% chance of a false-positive result. This means that about 19% of people who test negative are actually herpes positive.

A negative/normal test means you are considered herpes negative. But there is about a 38% chance that you got a false-negative test result. This mostly occurs when the test was done too early, before antibodies are produced.

What is an IgG titer and why does it fluctuate (goes up and down while staying in the positive range)?

A positive IgG test indicates the presence of a latent herpes infection. “Latent” means currently suppressed by a healthy immune system.

Once positive, it will stay positive for life. When the Herpes Select test is performed, in addition to a positive test results it gives an IgG number that fluctuates. We will explain here why that happens and the practical significance of it. Let’s start with the basics:

What is IgG?

We produce different antibodies in response to infection. The one we are interested in with regard to the herpes infection is IgG. This is the one that is checked for the presence of a herpes virus infection. It is not considered a protective antibody, as antibodies are in other infectious conditions.

The other antibody that is routinely checked for infectious conditions, called IgM, has no practical relevance in relation to a herpes infection and it’s not recommended that it be checked.

Once IgG-positive, always positive

Once IgG test is positive, it will always be positive unless it was one of a low number of the false-positive cases.

A long-term herpes study (https://sti.bmj.com/content/77/4/232) showed that if a person has a sufficient level of IgG antibodies, they will always have a detectable level of IgG antibodies, and if a person turned out to be IgG-negative in consecutive tests, that is merely due to a test error rather than a significant reduction of the IgG level (to the extent of becoming undetectable). Once a person is positive for herpes, they will stay positive for life.

Reason for fluctuations of the IgG level

The IgG antibody level increases with the amount of herpes virus in our body, but our immune system always tries to control the replication of the herpes virus. So, if a person has normally functioning immunity they will also have low levels of the herpes virus and stable levels of IgG antibodies. Any dysfunction of the immune system permits active replication of the herpes infection, resulting in increased levels of IgG antibodies.

So, if a person has decreased immunity (due to stress, injury, pregnancy, HIV, chemotherapy, etc.), they are likely to have an increased amount of the herpes virus and higher IgG levels.

The clinical significance of a higher antibody level

Fluctuations of the IgG level are a common concern of patients. The assumption at this point is that the higher the IgG level, the higher the chance of an outbreak and the higher the chance of transmission to other people (“silent shedding” of the virus).

What about discrepancies in different herpes tests: my herpes swab test came back negative, but my herpes blood test the same day is positive. How can that be?

Different herpes tests are done for different reasons. Tests should be done under ideal circumstances, but that’s not always the case. It’s difficult to answer this question based on available data, but I will make some fair assumptions from available data to attempt to explain this.

Assumptions

  • You have never before been diagnosed with herpes.
  • You had a sore that looked like herpes that could be swabbed.

Swab test

If you went to see a doctor with the skin lesion that looked like herpes and it was tested with the swab test, the test is testing only the skin outbreak. It tells you only if the skin outbreak was caused by herpes. If it’s negative, it means only that that particular lesion wasn’t caused by herpes but rather by something else. You could still have herpes that’s latent.

Blood test

If an IgG test was done the same day and was positive, it’s telling you that you have herpes that might flare up at any time, regardless of whether you currently have skin lesions caused by herpes.

Source

Slava Fuzayloff

By Slava Fuzayloff. D.O

Dr. Slava Fuzayloff is practicing STD physician with 20 years of experience and expert writer in the field of the sexually transmitted diseases.

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