HERPES - Lab Test and serology
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A herpes infection cannot be cured. After you become infected with HSV, the virus stays in the body for life.
HERPES SIMPLEX SEROLOGY
Dr.Deyn | 9 August 2019, Reviewed and updartred on 3 March 2021
DIAGNOSTIC TEST OVERVIEW
Herpes tests are done to find the herpes simplex virus (HSV). An HSV infection can cause small, painful sores that look like blisters on the skin or the tissue lining ( mucous membranes ) of the throat, nose, mouth, urethra , rectum, and vagina. A herpes infection may cause only a single outbreak of sores, but in many cases the person will have more outbreaks.
There are two types of HSV.
- HSV type 1 causes cold sores (also called fever blisters) on the lips. HSV-1 is generally spread by kissing or by sharing eating utensils (such as spoons or forks) when sores are present. HSV-1 can also cause sores around the genitals.
- HSV type 2 causes sores in the genital area (genital herpes), such as on or around the vagina or penis. HSV-2 also causes the herpes infection seen in babies who are delivered vaginally in women who have genital herpes. HSV-2 is generally spread by sexual contact. HSV-2 can sometimes cause mouth sores.
In rare cases, HSV can infect other parts of the body, such as the eyes and the brain.
Tests for HSV can be done using blood, urine, tears or spinal fluid. Different types of tests may be done.
- Herpes viral culture. This is a test to find the herpes virus. Fluid from a fresh sore is added to certain cells used to grow HSV. If no virus infects the cells, the culture is negative. If the herpes virus infects the cells, the culture is positive. The culture often fails to find the virus even when it is present ( false-negative results ).
- Herpes virus antigen detection test. Cells from a fresh sore are scraped off and then smeared onto a microscope slide. This test finds markers (called antigens ) on the surface of cells infected with the herpes virus. This test may be done with or in place of a viral culture.
- Polymerase chain reaction (PCR) test. A PCR test can be done on cells or fluid from a sore or on blood or on other fluid, such as spinal fluid. PCR finds the genetic material ( DNA ) of the HSV virus. This test can tell the difference between HSV-1 and HSV-2. Using the PCR test on skin sores isn't common.
- Antibody tests. Blood tests can find antibodies that are made by the immune system to fight a herpes infection. Antibody tests are sometimes done but are not as accurate as a viral culture at finding the cause of a specific sore or ulcer. Antibody tests cannot always tell the difference between a current active herpes infection and a herpes infection that occurred in the past. Because antibodies take time to develop after the first infection, you may not have a positive antibody test if you have just recently been infected.
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WHAT DOES A POSITIVE HERPES IgM TEST RESULT MEAN?
Question: Does a Positive Herpes IgM Test Mean I Was Recently Infected with Herpes?
Answer: Not really.
Many doctors will tell patients with a positive herpes IgM test that their test result means they were recently infected with herpes (HSV). This is because HSV IgM antibodies are thought to peak shortly after an initial infection and then recede. In fact, that is the common wisdom for IgM antibodies in general.
Compared to IgM, herpes IgG antibodies develop more slowly. However, they are expected to remain high throughout the course of an infection.Therefore, a positive HSV IgG test is thought to mean that the detected infection is at least several months old.
Interestingly, recent research suggests that the common wisdom about herpes blood test results may not be accurate. Individuals who were recently infected with herpes DO tend to have positive HSV IgM tests. However, so do many people with recurrent herpes infections. Between 30 and 70 percent of people with recurrent herpes are positive on HSV IgM tests, depending on the test and the study.
Herpes IgM tests are more likely to be positive in early herpes infections than herpes IgG tests. All this shows is that a positive herpes IgM test alone does not prove that an infection is recent. That's particularly true if it is accompanied by a positive herpes IgG test.
If you have a positive herpes IgM test and a negative herpes IgG test, then it is more likely that your results signal a recent infection. However, it is possible to misinterpret false positive test results. Therefore, if you have no symptoms, you may want to go back for IgG testing at a later date.
If you do have symptoms, your doctor can test the lesions for herpes directly. There is no need to wait for an antibody response.
Detectable levels of herpes IgG take longer to develop than detectable levels of herpes IgM. However, even herpes IgM antibodies can take up to ten days to develop after primary infection with the virus. Therefore, if you believe you have been exposed but have no symptoms, don't run to the doctor. It's best to wait at least two weeks before getting tested - or even longer, depending on which tests are available in your area. You may also want to go for a repeat test after 6 months if you do not undergo regular screening.
WHAT DOES A POSITIVE HERPES IgG TEST RESULT MEAN?
Herpes IgG tests are one type of blood test for the herpes simplex virus (HSV). Herpes blood tests look for the body's immune reaction to a herpes infection. They don't search directly for the virus. Because the immune reaction takes time to develop after the time of infection, it's not immediately detectable. In fact, depending on the type of test used, it can take up to four months to become positive on an HSV IgG test.
How Does an HSV IgG Test Work?
When a person becomes infected,the immune system tries to fight off the infection. That's true not just for herpes but for any pathogen, Part of that process involves the production of antibodies. These proteins are specific for each infection they are fighting.
For a new type of infection, it takes time for the body to make strong antibodies. The body can make several kinds of antibodies to fight infections. The two types that herpes blood tests look for are IgG and IgM. Herpes IgM antibodies usually are detectable by herpes blood tests within 7-10 days after initial infection. IgM levels stay high for approximately two weeks. After that, they usually decline.
Therefore IgM testing is primarily considered to be useful for detecting acute infection. However antibody levels also sometimes go up during an outbreak.
In contrast, herpes IgG antibodies do not show up until slightly later after initial infection. A positive herpes IgG test, if the test result is accurate, means that your body has been infected with the herpes simplex virus.
Furthermore, type specific herpes IgG tests can be used to distinguish between HSV-1 and HSV-2. Type-specific tests are far more accurate than non type-specific tests,However, they can not detect whether a particular infection is oral or genital. The only way to determine that is to watch for symptoms.
HSV-1 usually infects the mouth, causing oral herpes, and HSV-2 usually infects the genitals. However, there are a growing number of people with genital HSV-1. That's why herpes IgG and IgM tests can only tell you that you have been infected. They can't show where where.
HSV Blood Test Results & Timing of Infection
If you test positive for herpes IgG but not IgM, then your herpes infection is probably not recent. You've probably been infected for at least two months. Individuals with newer infections are more likely to test positive for both herpes IgG and IgM. They might also be positive for herpes IgM alone. The converse, however, isn't true. Positive herpes IgG and IgM results together do not necessarily mean you were infected recently. Between 30 and 70 percent of patients with recurrent herpes infections will test positive for herpes IgM.
| Positive IgG | Negative IgG | |
|---|---|---|
| Positive IgM | Infection date indeterminate | Acute/Recent infection |
| Negative IgM | Established Infection | No infection detected |
Test Accuracy
It is possible to have a false positive or false negative result. That's true for either a HSV IgG or HSV IgM test. Therefore, don't panic if your herpes blood test results do not agree with your known risk factors and sexual history. Instead, talk to your doctor about possible issues with testing. Diagnostic testing isn't perfect. You also may not be accurately assessing your risk. Many people do not understand that herpes can be transmitted even when their partner has no symptoms or does not know they are infected.
Sources:
Hashido M, Kawana T. Herpes simplex virus-specific IgM, IgA and IgG subclass antibody responses in primary and nonprimary genital herpes patients. Microbiol Immunol. 1997;41(5):415-20
Ho DW, Field PR, Sjögren-Jansson E, Jeansson S, Cunningham AL. Indirect ELISA for the detection of HSV-2 specific IgG and IgM antibodies with glycoprotein G (gG-2). J Virol Methods. 1992 Mar;36(3):249-64.
Morrow R, Friedrich D. Performance of a novel test for IgM and IgG antibodies in subjects with culture-documented genital herpes simplex virus-1 or -2 infection. Clin Microbiol Infect. 2006 May;12(5):463-9.
Morrow RA, Friedrich D. Inaccuracy of certain commercial enzyme immunoassays in diagnosing genital infections with herpes simplex virus types 1 or 2. Am J Clin Pathol. 2003 Dec;120(6):839-44.
Page J, Taylor J, Tideman RL, Seifert C, Marks C, Cunningham A, Mindel A. Is HSV serology useful for the management of first episode genital herpes? Sex Transm Infect. 2003 Aug;79(4):276-9.
Hashido M, Kawana T. "Herpes simplex virus-specific IgM, IgA and IgG subclass antibody responses in primary and nonprimary genital herpes patients." Microbiol Immunol. 1997;41(5):415-20.
Ho DW, Field PR, Sjögren-Jansson E, Jeansson S, Cunningham AL. "Indirect ELISA for the detection of HSV-2 specific IgG and IgM antibodies with glycoprotein G (gG-2)." J Virol Methods. 1992 Mar;36(3):249-64.
Morrow, R. and Friedrich, D. "Performance of a novel test for IgM and IgG antibodies in subjects with culture-documented genital herpes simplex virus-1 or -2 infection" Clin Microbiol Infect 2006; 12: 463–469
Page J, Taylor J, Tideman RL, Seifert C, Marks C, Cunningham A, Mindel A. "Is HSV serology useful for the management of first episode genital herpes?" Sex Transm Infect. 2003 Aug;79(4):276-9.
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