What Can Cause a False Positive Herpes Test Result? 5 Common Reasons You Should Know

Herpes is a common condition, with 50-80% of American adults carrying oral herpes (HSV-1) and 11.9% having genital herpes (HSV-2). It’s a condition often associated with discomfort and stigma, which makes accurate testing crucial.

But what happens if your herpes test result is a false positive? Imagine the emotional turmoil of believing you have herpes, only to later find out the diagnosis was incorrect. This situation is more common than you might think.

So, what can cause a false positive herpes test? Let's explore the reasons and how you can handle such a scenario.

What Can Cause a False Positive Herpes Test? 5 Common Reasons

Several factors can potentially contribute to incorrect herpes test results even when the person has no herpes simplex virus (HSV). Those include:

1. Type of Test

• Several types of tests (e.g., Herpes Simplex Virus (HSV) IgG blood test, Herpes IgM blood test, Viral culture, and Polymerase Chain Reaction (PCR) test) are used, and not each one of them is equally accurate.

• For instance, the HSV IgM blood test is less accurate compared to the IgG blood test and gives more false-positive results, particularly for HSV-1.

• The reasons are that the HSV IgM blood test can't precisely differentiate between HSV-1 & HSV-2 antibodies, detects antibodies (that may not be for herpes) early, and can undergo cross-reactivity with some other viruses. 

2. Test Timing

• If it is the early stage of herpes infection (they haven't developed a noticeable outbreak), the immune system of the body might not yet release sufficient detectable antibodies.

• Taking the test, particularly the IgM blood test early, can mistakenly identify those non-specific antibodies as a possible sign related to a herpes infection.

• This can lead to incorrect herpe test results - false positives (more rarely) and false negatives. 

3. Laboratory Errors

Sometimes, laboratory errors can be the culprit. Those blunders can occur during the testing procedure, such as:

• Mistakes while handling, storing, and processing the samples

• Mislabeling the samples

• Contamination

• Incorrect evaluation

• Lab technician error

All these factors are possible and can contribute to false-positive results. 

4. Cross-reactivity

• In some cases, the test might react with proteins or antibodies from other viruses that may be similar to herpes viruses.

• For example, an individual with Epstein-Barr virus or varicella-zoster virus due to viral infection may produce antibodies that can cross-react with herpes simplex virus (HSV).

• This may lead to misinterpretation of the herpes test results, especially when the antibodies share the same structure.

5. Underlying Health Issues

• Sometimes, certain medical conditions like autoimmune disorders or chronic infections can contribute to false-positive herpes test results.

• These health conditions can affect the immune system of the body and trigger the release of high or unusual levels of antibodies.

• This may interrupt the accuracy of the herpes test, resulting in a false positive result. 

What to Do In Case of a False Positive Herpes Test Result

If you receive false positive results, firstly, stay calm and avoid panicking. Here's what you can do:

• Request Additional Testing: Go for an additional confirmatory test, like a polymerase chain reaction (PCR) test or a second antibody test. This helps confirm the result with accuracy.

• Consult the Doctor: Discuss your test results and all your symptoms with the doctor. They can better help with the proper guidance toward the appropriate diagnosis.

• Consider Your Risk Factors: If you have any sexual history & risk factors that can raise the risk of actual exposure to HSV, speak about it to your doctor.

• Look for a Second Opinion: If you are still unsure or not completely satisfied with the given explanation regarding the result, go for a second opinion for more clarity.

• Understand the Test Limits: Remember, false positive results are common, particularly with antibody blood tests. So, always discuss the different tests before deciding. 

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FDA Recommendations 

The U.S. Food and Drug Administration (FDA) recommends that all healthcare providers & lab staff be aware of the following things to lower the chances of false reactive results:   

• Check the CDC guidelines before advising HSV-2 blood tests.

• Be mindful that false positive results can occur.  

• Guide the people regarding the drawbacks of available tests before getting HSV-2 serologic tests. 

• Perform additional confirmatory testing, like Biokit or Western blot tests, for false positive results as given in the labeling of the test and according to professional guidelines.

Why Do False Positives Happen More Often?

False positives happen more often due to the early blood test and the low risk of herpes infection. The test results are common, giving half of the incorrect results. Serology (antibody) Tests like the HerpeSelect test can produce around 50% incorrect false positives. Hence, better useful for detecting past herpes infections even in the absence of symptoms.

The inaccuracy is primarily because of "borderline positive" readings, which fall close to the standard test's cutoff for a positive diagnosis. This can lead to misinterpretation of the result.

How Long to Wait Before Herpes Tests?

To get a conclusive result of the herpes test, the waiting period can depend on the type of test:

Blood Test:

• Up to 12 weeks after the last exposure to the herpes viruses.

• For some people, their body may take a longer period to release detectable antibodies. So, if the initial blood test report is negative, it is rescheduled after 6 months.

Polymerase Chain Reaction (PCR) Swab Test (for visible sores):

• Within 2 hours of the appearance of sores.

• This herpes test is less accurate if sores are extremely small or start healing.

Important Notes:

• Herpes's incubation period (time from exposure to onset of symptoms) is usually 2 to 12 days, but some individuals might not develop any symptoms for months or years.

• Early testing before the antibodies develop or sufficient viral load is available for the Polymerase Chain Reaction (PCR) Swab Test, the result can be false negative.

• The best advice is to get a PCR swab test immediately when you experience active sores. But, if there are no symptoms, wait for about 12 weeks after the possible exposure to the herpes viruses for an accurate blood test result. 

Comparing Tests for Genital Herpes With or Without Symptoms

When Should You Consider a Herpes Test?

Get tested for herpes if you:

• experience any genital symptoms that can be associated with herpes.

• have or had a sex partner living with genital herpes.

• have multiple sex partners, to get tested as part of comprehensive sexually transmitted disease (STD) screening.

• have herpes symptoms examined by your doctor, but still need a confirmatory test.

Testing allows doctors to understand what can happen in the future and what treatment plan can help. Medications can help reduce symptoms. In addition, doctors can guide you on how to prevent the risk of herpes transmission to your partner.

Moreover, herpes testing is not recommended for individuals with no symptoms in certain situations. That's because of the limitations of the blood tests and the chances of incorrect results. The possibility of false herpes test results is higher in people with low infection risk.

READ ALSO Step-by-Step Guide: How to Get Tested for Herpes

Can Herpes be Actually Misdiagnosed?

Yes, misdiagnosis of herpes can occur due to the following reasons:

• Similar Symptoms

Conditions such as genital warts, fungal infections, or ingrown hairs can imitate the symptoms of herpes, causing confusion.

• False Positive Results

Lab errors, cross-reactivity with other present viral infections, or incorrect sample collection can contribute to a false-positive herpes test result.

• Lack of Symptoms

Some individuals may not show noticeable herpes symptoms, resulting in missed diagnosis and associating those symptoms with other issues.

• Initial Outbreak Confusion

The first herpes outbreak may be mistaken for other conditions, as the sores at an early stage might be different in appearance or less extreme.

• Overlapping Infections

People who are also living with other infections, such as sexually transmitted infections (STIs), might experience overlapping symptoms, making the diagnosis complicated.

• Test Timing

Too early or too late testing during the herpes infection cycle can impact the results' precision, especially in the antibody blood tests.

Herpes can be mistaken for the following conditions:

• Other STIs: Syphilis, chlamydia, trichomoniasis, chancroid, genital warts (HPV), and Lymphogranuloma venereum.

• Skin irritations: Razor bumps, irritation related to shaving, and ingrown hairs.

• Skin conditions: Yeast infections, bacterial vaginosis, and genital eczema.

• Canker sores: Painful sores or bumps in the mouth.

Final Thoughts

For those wondering, what can cause a false positive herpes test result, well, factors like test types, lab errors, cross-reactivity, or other health issues can contribute to it. Though they are not common, they can be a possibility. Hence, understanding the potential reasons behind such a misinterpretation and seeking confirmatory tests is crucial if you are unsure.

Remember not to panic in case you get positive results. See a doctor to ensure a precise diagnosis. Stay informed & take proactive measures for good health!

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