Blood test for genital herpes virus

In general, samples taken for isolation or antigen detection are also suitable for DNA detection methods. The enhanced sensitivity of methods based on nucleic acid amplification above other direct methods culture or antigen detection ensures that even lesion samples containing minimal cells can be analyzed with good sensitivity.

Approximately 8 mL to 10 mL of blood is usually collected in tubes without anticoagulant or preservatives. After the blood has clotted at room temperature, the serum is separated by centrifugation and removed to another vial. Whole blood should not be frozen because the cells will hemolyze, making the specimen unsuitable for serological testing.

In general, a single specimen is preferred, but acute and convalescent sera collected six to eight weeks apart may be preferred in select situations Direct tests endeavour to demonstrate the presence of HSV in a suspicious lesion or in genital secretions. Ideally, the sample should be taken from a vesicular lesion that has been present for less than 24 h because once the lesion has begun to crust, the test sensitivity will decline.

If multiple vesicles are present, more than one lesion should be sampled. In addition, test sensitivity is lower in patients with recurrent lesions than in those with first episodes Tube culture isolation is the traditional gold standard for HSV detection and the reference method against which all other tests are measured 16 , Once received in the laboratory, the specimen should be vortexed.

The swab should then be removed from the transport medium and firmly rolled against the inside of the tube to express as much fluid as possible. Some laboratories may add an antibiotic preparation to the primary samples before inoculation into cell culture.

The specimen may be inoculated into the culture medium or may first be adsorbed onto the cell monolayer after removal of the medium Adsorption facilitates more direct contact of viral particles with the cells and enhances infectivity, increasing both the number of isolates and the speed with which they are recovered.

The first two are used most often because of their increased sensitivity compared with the other cell lines 20 , Although HSV isolation times vary depending on the condition and sensitivity of the cell lines used for isolation and the amount of infectious virus present, most isolates will show visible cytopathic effect CPE after two to three days of cultivation.

The cell culture monolayers should be examined daily for evidence of CPE. Cultures should be held for seven to 10 days, depending on the cell line used. The CPE starts focally but spreads rapidly to affect other parts of the monolayer. Occasionally, multinucleated giant cells may be present. Some laboratories include a DFA procedure using monoclonal antibodies in their virus isolation algorithm to confirm and type the isolate in a single step.

Many laboratories now use centrifugation-enhanced shell vial culture methods to reduce viral isolation times The same specimens used for traditional viral culture methods may be used for shell vial cultures. Shell vial culture can reduce viral isolation times from one to seven days to a duration of 16 h to 48 h.

However, although these methods are rapid and specific, they are slightly less sensitive than traditional tube cultures and are more expensive Although a number of cell lines may be used, MRC-5 cells are used most often. Because of the reduced sensitivity of the shell vial method, it has been suggested that an additional standard tube culture should be inoculated in parallel for each specimen.

Replication of HSV in these cells induces galactosidase production, and infected cells stain blue when overlaid with an appropriate substrate. Typing can then be performed using type-specific antisera on any monolayers showing blue cells. As discussed previously, the serotype of HSV responsible for infection can have prognostic implications. Therefore, if typing is not done routinely, the isolate should be saved until it is determined whether typing is required or not.

The reporting of type-specific HSV will aid the clinician in counselling and management of the patient. Viral antigen detection may be a suitable alternative to culture for smaller laboratories in which the expense of maintaining cell lines is unwarranted.

Antigen detection is also an alternative where specimen handling and transportation conditions could inactivate any virus present. This could occur, for example, in laboratories serving remote locations with prolonged specimen transportation times under uncertain conditions. For detecting HSV in lesions, the sensitivity of antigen detection tests may be the same as or greater than that of culture 24 , Detection of HSV antigens has been achieved in fixed cells by DFA tests or immunoperoxidase tests on fixed, solubilized cell specimens 24 - These methods can give a useful result even in the absence of cultivable virus.

The demonstration of the presence of HSV antigen by DFA staining of smears can provide a rapid adjunct to cell culture. Although the slide may be prepared by the clinician, it is ideally prepared by the laboratory using a cytospin method and a swab specimen collected as described earlier.

Staining of the slide is as directed by the manufacturer of the fluorescein-labelled antibody. The slide is examined using a fluorescence microscope, with a positive test indicated by the presence of a characteristic pattern of apple-green fluorescence in the nucleus and cytoplasm of the basal and parabasal cells.

Only intact cells should be examined. An inconclusive result may be obtained if fewer than 50 intact cells are present on each well. HSV infection causes typical cytopathic changes in genital epithelial cells 3. The cells become enlarged, with intranuclear inclusions, often with the formation of multinucleated cells.

Prepared slides are stained with a Wright-Giemsa stain and then examined under light microscopy. Hematoxylin and eosin or the Papanicolaou stains may also be used. This test can be performed when an urgent result is needed and no alternative test is immediately available, but it does not negate the need for follow-up testing of all negatives with a more sensitive test.

Direct examination of vesicle fluid or other clinical material by electron microscopy for the diagnosis of HSV is limited by the fact that viral morphology cannot be used to distinguish HSV from other herpes viruses eg, varicella zoster virus Viral DNA may be detected by hybridization techniques using radiolabelled or biotinylated probes 27 , These methods have largely been superceded by more sensitive and less laborious procedures which utilize amplification of the target HSV DNA by polymerase chain reaction PCR.

Specificity of the amplification method is assured by either undertaking a second PCR with target-specific primers nested PCR or by HSV-specific probe hybridization of amplified products. The majority of laboratories have confined their use of methods such as PCR to the investigation of suspected HSV encephalitis In this situation, the enhanced sensitivity over culture- or antigen-based procedures is well-recognized, and the clinical value of positive results is clearly demonstrable.

In the case of possible genital herpes, PCR detects viral DNA for several days after lesions do not contain demonstrable infectious virus This may mean that a laboratory switching to sensitive procedures based on nucleic acid amplification may have an increased number of positive results on lesion samples with possible clinical dilemmas regarding the relevance of positive results obtained after treatment. Although PCR can detect HSV DNA from later stages of lesions than virus culture, there is a theoretical risk of false-positive results occurring due to sample contamination before amplification.

Laboratories undertaking PCR-based procedures need to have separate areas and equipment for pre- and postamplification handling of specimens to minimize this kind of problem. Samples giving discordant results eg, positive by PCR and negative on culture are usually confirmed by a second PCR directed to a different gene to ensure assay specificity.

As with other molecular diagnostic tests, the sensitivity of PCR is much greater than the gold standard of culture 31 - The advent of real-time PCR systems, where products are detected in a closed-tube system without any post-amplification handling, has minimized the risk of false-positive results by PCR. While the equipment to undertake real-time PCR is still relatively expensive, the small reaction volumes and minimal technical hands-on time particularly when kit-based reagents are used make these methods very cost effective for many laboratories.

The detection of antibodies to HSV allows for diagnosis when other virological methods cannot be performed or yield negative results It is particularly useful in identifying the asymptomatic carrier of infection because, as discussed above, the majority of transmission occurs while the person is asymptomatic.

Thus far, the use of these tests has largely been confined to seroepidemiological studies and case management for HSV, while specific clinical uses for serological testing remains a much debated topic.

Clinical, virological and serological classification of infection with genital herpes simplex virus HSV. Serological assays that are not type-specific have limited clinical utility. In addition, no serological test is able to differentiate between oral and genital infection with HSV. This difference has been exploited in developing type-specific serological tests.

A recent review describes the new HSV type-specific antibody tests Finally, it appears that seroreversion or waning of immune response to gG-2 occurs with time, raising concerns about the long-term reliability of these tests This test is expensive, time consuming and requires skilled interpretation.

When initial results are indeterminate or atypical, adsorption of sera with type-specific antigen and reblotting can sometimes 'clean up' the blot and improve interpretation. Although most of the available literature evaluating the performance of type-specific tests was based on kits developed by Gull Laboratories USA , these tests have now been withdrawn from the market.

Presently, two companies produce four kits for the diagnosis of HSV type-specific antibodies. A number of antiviral agents have been developed for the management of HSV infections; of these, acyclovir is the most commonly used.

Resistance of HSV to acyclovir has become increasingly common, with almost all clinically significant acyclovir-resistant strains seen in immunocompromised patients, especially those coinfected with HIV 43 , The development of resistance usually results from mutations within the viral genome, and the presence of selective drug pressure usually results in the emergence of a resistant virus population.

The isolation of HSV from persisting lesions despite adequate dosages and blood levels of acyclovir should raise the suspicion of acyclovir resistance. The antiviral activity of acyclovir requires an initial phosphorylation step by the viral enzyme thymidine kinase TK 45 , Two subsequent phosphorylation steps are mediated by cellular kinases.

The resulting triphosphorylated acyclovir then specifically inhibits herpesvirus DNA polymerases. Three different mechanisms of resistance of HSV to acyclovir have been identified. The most common is found in viruses that lack a functional TK TK - mutants and, thus, are unable to monophosphorylate acyclovir. Less commonly, some resistant viruses produce a functional TK enzyme that is unable to phosphorylate acyclovir because of altered substrate specificity TK A mutants. Foscarnet directly inhibits herpesvirus DNA polymerases and resistance develops because of altered viral DNA polymerases.

Vidarabine resistance also occurs rarely. Vidarabine is phosphorylated by cellular enzymes and then inhibits virally encoded DNA polymerase.

The complexity of drug sensitivity assays for antiviral resistance limits their availability. At the present time, they are only performed by specialized laboratories. Susceptibility testing of strains of HSV against various antiviral agents is usually performed in the laboratory using modifications of one of the following: plaque reduction assays, dye uptake assays or DNA hybridization assays 45 , The plaque reduction assay was the first antiviral susceptibility testing method performed to determine the susceptibility of viruses to antiviral agents and is the standard against which other tests are compared.

These tests are time consuming and may soon be replaced by genotypic tests that can be processed more quickly. All laboratories providing diagnostic services for the detection of HSV in clinical samples or performing HSV serological assays must participate in the testing of proficiency panels provided by external agencies whenever possible for all tests performed.

If proficiency testing for specific assays is not available eg, HSV DNA detection in swab material or type-specific serological testing , then specimen exchange among laboratories performing such testing should be arranged as an alternative form of proficiency testing. Subpassages of HSV clinical isolates should be inoculated with each batch of HSV roller tube or shell vial cultures to serve as positive controls. Upon arrival at the testing site, you will be asked to register, sign a consent form, and possibly confirm your insurance information.

Because genital HSV is not what's called a notifiable disease , like HIV or hepatitis, your information and results will not be shared with local, municipal, state, or federal health authorities. Some STI clinics will conduct a short pre-test counseling. The aim of the counseling is to establish why you feel you need the test and whether you may be at risk of other STIs. Based on your response, the counselor may recommend additional STI screening. The recommendations do not have anything to do with you personally.

They are based on guidelines for all people in highly affected populations. This includes chlamydia and gonorrhea testing for sexually active women under age 25, women ages 25 and older, and men with certain risk factors. They may also offer HIV testing, which is recommended once for all people ages 15— An HSV blood test is a simple blood draw involving the following steps:. You will have a small puncture wound at the injection site. This should stop bleeding within a few minutes.

Leave the bandage on for about one day to prevent infection. Light-headedness and infection are rare but also possible. Your test results should be ready within two to five working days.

Timing may vary depending on the clinic or lab. The results of your HSV blood test will generally be reported as either:. If your test is equivocal, your healthcare provider might consider results of other tests you've had done to make your diagnosis. They might also recommend that you repeat the IgG test after a few weeks. IgG results may be considered along with IgM results. IgG antibodies take longer to produce but last a lifetime. IgM antibodies are detectable after a few days, but they disappear within a few weeks.

A false-negative result , in which your test result is incorrectly reported as negative for HSV antibodies, can sometimes occur. This happens, for instance, if you have your test within the window period, not allowing enough time to pass after a possible exposure. You may also have a false-positive result, in which the test result incorrectly reads as positive.

An IgG blood test is used to diagnose herpes simplex virus infection. It detects the antibodies your body produces to fight against the virus. Test results are ready within two to five working days. If you have symptoms of HSV, it's important that you get medical attention. Your healthcare provider can examine you and order the appropriate tests. It can be overwhelming to even think about the possibility of an HSV diagnosis.

But if you are positive, know that you are not alone. It is important to remember that you can live a long and happy life with herpes. Seek treatment early and follow your healthcare provider's guidance on safer sex. Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life.

Centers for Disease Control and Prevention. Genital herpes screening FAQ. Diagnosis of genital herpes simplex virus infection in the clinical laboratory. If you have a partner with genital herpes, testing can tell if you also have the virus. If you are not infected, your doctor can talk to you about ways to lower your risk of getting genital herpes. If you are a pregnant woman and have a partner with genital herpes, it is very important to get tested.

If you get genital herpes during pregnancy your baby could also become infected. Herpes infections in babies can be life-threatening. If you are infected, your doctor will talk to you about your diagnosis and the possible symptoms of genital herpes. In addition, herpes blood testing may be useful if you are seeking a complete STD exam, especially if you have multiple sex partners.

Herpes blood tests may or may not be included. Your doctor chooses STD tests based on your sexual behaviors number of sex partners, if condoms are used every time, etc. This is why you should have an open and honest discussion with your doctor about your sex practices and history. When you go in for STD testing, it is important to ask your doctor which infections you are and are not being tested for, and why.

STD tests are usually done for infections that have serious outcomes if they are not treated. For example, finding and treating curable STDs like chlamydia can stop them from causing serious complications like infertility the inability to get pregnant in women.

Genital herpes does not usually result in serious outcomes in healthy, non-pregnant adults. More often, the stigma and shame from a genital herpes infection can be more troubling to someone who is infected than the disease itself.

If you are worried about genital herpes, you should talk with your doctor about whether you should be tested. There is no evidence that diagnosing genital herpes with a blood test in someone without symptoms would change their sexual behavior and stop the virus from spreading. In addition, without knowing the benefits of testing, the risk of shaming and stigmatizing people outweighs the potential benefits.

For these reasons, testing everyone for herpes is not recommended at this time. Even though adults with genital herpes may not have any symptoms, herpes infections in babies can be life-threatening.

Women who get genital herpes during late pregnancy have a very high risk for having a baby with herpes infection, and these women may not even know they are infected.