Can you test negative for herpes after testing positive

In this section, we’ll give you information about herpes testing.

Testing is what ultimately establishes or rule out a diagnosis of herpes. All the other we’ve talked about—what you feel, what you see, and your odds of getting it—help us with the diagnosis, but they’ve can’t establish it or confirm it.

This section will summarize the different types of herpes tests, their accuracy, how they’re interpreted, and when they’re necessary. Tables with important statistics will be followed by FAQ answered by “Dr. F,” an STD expert.

So, if you want to know all about herpes testing, this chapter is for you!

The accuracy of various herpes tests

This table summarizes the overall accuracy of different herpes tests. Please especially pay attention to the most common test, the IgG test—and most importantly to its false positive and false negative rates.

The table has three columns:

• Test accuracy: how accurate is the test in detecting the herpes virus
• False positive: the test detects the presence of herpes, but the person doesn’t actually have it
• False negative: the test doesn’t detect the presence of herpes, but the person does have it

Please note: the numbers in the table are averages and may vary from case to case based on factors such as when the test is performed (during an outbreak or not), the testing technique, and the herpes viral load.

* The Washington University (Western blot) test is considered the “gold standard” blood test. The false-negative and false-positive rates for the commercially available IgG test are based on a comparison to the Western blot (reference test) results of the Washington University test.

When are herpes tests accurate?

In the table below, we summarize information about the timing of herpes testing.

One of the most important factors in any infectious disease testing is doing it at the right time. This means two things in the case of herpes:

• For the blood test to be accurate, the right amount of time needs to have passed
• The swab test should be done while symptoms are “fresh”

For each available herpes test, we will mention:

• The earliest testing time (the earliest the test can be performed)
• The ideal testing time (the time when the test is definitive and best done)

Frequently Asked Questions

Here we summarize real patients’ questions, grouped by topic, and Dr. Fuzayloff’s answers to them. “Dr. F” (his patients’ name for him) has been an STD doctor for over two decades in Midtown Manhattan, NYC.

• Is herpes screening necessary and routinely done?

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

  According to the CDC, 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 STD screening.

  Here is why herpes is not routinely tested for:

  1. 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.

  2. Testing will not change sexual behavior

  According to the CDC, there is no proof of a herpes-positive person changing their sexual behavior (switching to protected sex, practicing abstinence) after learning about their herpes status

  3. 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.

  4. 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.

  5. There is a chance of a false-positive result

  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.

• Why is the IgG herpes test the most commonly performed herpes test?

  The IgG test is also known as the herpes select 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.

• How is the Washington University herpes test different? Is it difficult to get it done?

  The Washington University HSV test is considered the “gold standard” herpes blood test because it has:

  • Better accuracy
  • 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 the table 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.

  Parameters	IgG—HerpesSelect®	Washington University (Western blot)
  Accuracy	97%–98%	> 99%
  Collection method	Blood test	Blood test
  Insurance coverage and cost	Covered by Insurance If no health insurance, out-of-pocket cost is about $70	Usually not covered by health insurance Out-of-pocket cost is about $130 (test only) There will also be a charge for a doctor visit to collect the blood and have the test ordered
  Where it’s done	Most healthcare facilities: STD clinics PCPs urgent care clinics women’s health clinics hospitals	University of Washington Virology Department (specimen collected at the point of service and send to UW)
  Time to get results	Usually, 3–4 days	May take more than a month for the entire process: contacting the university to get a kit seeing a doctor for blood draw sending a kit back getting your results

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

• How is the herpes culture (swab) test different from blood tests? How accurate is it, and how is it done?

  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 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 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.

  
  

  Parameters	HerpesSelect®	Culture
  Test accuracy	97%–98%	100%
  Timing	Can be done: anytime to confirm herpes status 3 weeks after exposure to confirm recent contraction	Can be done only during an outbreak
  Collection method	Blood test	Blister (ideally) should be broken and swabbed Sores that are not crusted can be swabbed (not ideal)
  Insurance coverage and cost	Covered by insurance If not insured, out-of-pocket cost is $70 (for the test); a one-time office visit fee will also be charged	Covered by health insurance If not insured, out-of-pocket cost is $130 (for the test); a one-time office visit fee will also be charged
  Testing facilities	Most healthcare facilities: STD clinics, PCPs, urgent care clinics, women’s health clinics, hospitals	Mainly STD clinics and hospitals (most non-specialized healthcare facilities do not carry the kit)
  Time to get results	3–4 days	4–7 days

• Choosing the right herpes test after exposure

  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?

  1. 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.

  2. 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.

• Is herpes testing covered by health insurance? When it’s not, what’s the out-of-pocket cost

  The commercially available IgG antibody testing (not the Washington University HSV test) and the culture swab test are typically covered by health insurance.

  If you want to be certain that your insurance covers it, call your insurance company and ask:

  1. What their preferred lab is (that is, what testing labs have contractual prices with your health plan; for example, Quest, LabCorp, Northwell)

  2. If the herpes culture test or herpes IgG test is covered; if the insurance rep asks you for ICD and CPT codes, give them the following codes:

  • ICD B00.9
  • CPT 86695 or 86696

  3. What the patient’s responsibility is for the test (any deductibles or coinsurance amounts)

• What are the common and official names for the different herpes tests?

  In the table below, we summarize the common and official names for herpes tests:

  Common name	Laboratory official name
  Washington University HSV test	Western blot
  Herpes IgG test	HerpeSelect ®
  Herpes culture test (swab)	ELVIS ®

• How accurate are the different 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.

  Here are more details:

  The culture test

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

  2. 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)

  3. Is more reliable during the first outbreak

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

  The IgG test (HerpeSelect 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. 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 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

  HerpeSelect 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 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 (HerpeSelect) 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.

• Interpretation of herpes tests

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

  In this table, we tell you what positive and negative results for each test mean (assuming that the test was done under ideal conditions at the right time for that test (see the discussion above).

  Test	Positive	Negative
  Culture	You may be 100% sure that you are herpes-positive and that your skin lesion is herpes.	The skin that was swabbed is not a herpes lesion. It 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.) There is always a chance that not enough sample was collected; 25% of herpes swab tests are considered false negatives
  Commercially available IgG	You are most likely herpes-positive. There is a 19% chance of a false-positive result. This means that about 19% of people tested negative are actually herpes-positive.	You are considered herpes negative. There is about a 38% chance that you got a false-negative test result.
  Washington University HSV	You are most likely (> 99%) herpes-positive.	You are most likely (> 99%) herpes-negative.

• 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 HerpeSelect 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 culture 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.

• 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 STD and known as “genital” herpes.

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