Who Needs Serum Testing for Genital Herpes?

Anne L. Teitelman, PhD, CRNP

Disclosures

February 16, 2011

Question:
When is it appropriate to obtain a serum test for genital herpes?

Response from Anne L. Teitelman, PhD, CRNP
Assistant Professor, Family and Community Health Division, School of Nursing, University of Pennsylvania, Philadelphia, Pennsylvania; Nurse Practitioner, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania

Most genital herpes is caused by herpes simplex virus type 2 (HSV2), although type 1 (HSV1) can also cause genital herpes infections. However, HSV1 more typically causes "cold sores" (oral herpes). HSV2 is transmitted through sexual contact including skin-to-skin contact with a partner who is shedding the virus.[1] Shedding more often occurs around the time of an outbreak, but can also occur when an infected individual has no symptoms.[2] Condoms can reduce sexual transmission of HSV2 by 50%. HSV2 can also be spread vertically from mother to child.[1]

Genital herpes infections commonly present as painful sores or ulcers, but often symptoms are more subtle, for example, itching, burning, tingling, redness, fissures, or pain in and around the genital area, buttocks, or upper thighs that are often not recognized as a herpetic outbreak. Furthermore, many individuals affected by genital HSV2 are asymptomatic.[2]

The prevalence of HSV2 in the general adult population is 20%, but some groups are disproportionately affected. The rate of HSV 2 among black adult women is 50%.[3] However, of those with HSV 2, only 10%-25% are aware that they have genital herpes, thus most transmission occurs from people who are unaware that they are infected.[1] HSV2 is more likely to be associated with recurrences and asymptomatic viral shedding, compared with HSV1, and thus it can be helpful to distinguish HSV1 from HSV2 infections for making treatment decisions and determining prognosis.

Testing and diagnosis. HSV1 and HSV2 are initially diagnosed clinically and should be confirmed with laboratory testing. HSV virologic tests can be obtained with a swab from the ulcer and include viral culture, which has a low sensitivity, and polymerase chain reaction assays, which are more sensitive. According to Centers for Disease Control and Prevention (CDC) guidelines, virologic tests are preferred for patients seeking treatment for genital ulcers, but a negative result does not indicate a lack of infection because shedding is sporadic.[4]

In addition, tests for other causes of genital lesions should also be performed, such as testing for Treponema pallidum, which causes syphilis. A type-specific IgG serum test can now differentiate HSV1 infections from HSV2 infection with 97%-100% sensitivity and 94%-98% specificity.[1] If antibodies are detected, this can indicate a recent or previous exposure, because once a person is infected, the virus stays in the body. However, there is a chance of false-positive results, especially among those with a lower risk for acquiring HSV infection. Serologic tests are most accurate 12-16 weeks after initial exposure to the virus, because it takes several weeks for antibodies to develop. Thus, a false-negative result could occur if a test is obtained before this time.

Recommendations for HSV2 screening. According to the recently released sexually transmitted disease (STD) treatment guidelines,[4] HSV type-specific tests may be useful in specific clinical situations:

  • Patients who have had recurrent genital symptoms but negative herpes virologic tests;

  • Confirming infection in people who have been diagnosed clinically with genital herpes;

  • Determining if the partner of someone diagnosed with genital herpes has acquired herpes;

  • Patients presenting for STD testing (especially if they have multiple partners); and

  • Patients with HIV infections and men who have sex with men who are at increased risk of acquiring HIV infection.

The CDC does not recommend screening for HSV1 or HSV2 in the general population.[4]

Benefits and drawbacks to HSV2 serum testing. The benefits are clear. A person who is aware of his or her HSV2 positive status may be more likely to take precautions to prevent transmission to sexual partners. Also, by practicing safer sex, people with HSV2 infection are less likely to acquire HIV. Having HSV2, even without symptoms, increases the risk of acquiring HIV by 2- to 3-fold.[1,5] In pregnant women, knowledge of the specific HSV type may be helpful in reducing the chance of transmission to the neonate. Therefore, if an HSV2 test is clinically indicated, general STD prevention counseling and HSV2 specific information are provided. General counseling usually includes discussion of sexually transmitted infection behavioral risk reduction (using condoms, limiting number of partners) to reduce the chance of transmission to a sexual partner and a discussion of what testing for other sexually transmitted infections will be recommended. HSV2-specific information includes a review of common HSV2 presentations to increase awareness of the more subtle symptoms and preparation for disclosing HSV2 status to sexual partners.

Obtaining false-positive results is the major drawback to type-specific testing for genital herpes. Even though sensitivity and specificity of the type-specific serum tests are high, the predictive value of the tests may be low if the prevalence is low.[6] Even in STD clinics, 10% may be wrongly diagnosed and in lower risk populations this rate could be as high as 30%-40%.[6] These tests could be verified with Western blotting. However, the Western blot test for HSV2 is expensive and may not be widely available.[6]There is still considerable stigma associated with genital herpes and the psychological effect of receiving a diagnosis of genital herpes can be substantial,[4] which raises ethical concerns when the level of wrong diagnosis is high.[6]

For management of HSV2 and HSV1, see the 2010 STD treatment guidelines.[4]

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