Check herpes tests — Some may be inaccurate
If your clinic uses an outside laboratory, do you know what test is used to diagnose herpes simplex virus type-2 (HSV-2), which causes genital herpes? According to a just-published journal article, many U.S. laboratories are using outdated blood tests that often produce false-positive results.1
Researchers from the University of Washington in Seattle examined results from proficiency testing performed by the Northfield, IL-based College of American Pathologists (CAP). In the CAP testing, 172 participating laboratories were sent a sample of blood that was positive for HSV-1 antibodies, which cause common "cold sores," and negative for HSV-2 antibodies. While almost all of the laboratories accurately detected HSV-1 in the sample, more than half incorrectly reported that the sample was positive for HSV-2 antibodies.1
"The point of the article is that the vast majority of laboratories in the United States still use old serologic tests, which do not distinguish oral herpes from genital herpes," says the study’s lead author, Zane Brown, MD, professor of maternal-fetal medicine in the department of obstetrics and gynecology at the University of Washington in Seattle. "The social and medical consequences of using one of these serologic assays that do not distinguish oral from genital herpes to test a patient are numerous and severe."
According to the Centers for Disease Control and Prevention (CDC), at least 45 million people ages 12 and older, or one out of five adolescents and adults, have had genital HSV infection. Between the late 1970s and the early 1990s, the number of Americans with genital herpes infection increased 30%, says the CDC.2
If the test used by clinicians does not clearly distinguish oral from genital herpes, then 75% of patients screened with the test will appear inappropriately to be infected with the genital form of the virus, says Brown.
Accuracy is key
According to the Research Triangle Park, NC-based American Social Health Association (ASHA), there are many older blood tests commercially available to test for HSV; however, most are not accurate because they cannot accurately distinguish between antibodies for Type 1 and Type 2 herpes. For many years, ASHA has been concerned about promoting accurate diagnostic testing and creating access to the truly type-specific serologic tests, says Charles Ebel, vice president of ASHA’s health program resources.
Herpes simplex virus is an infection that often has mild, unrecognized symptoms, so to progress in prevention requires doing better case identification, he states. Apart from its putative public health value, accurate herpes testing is something that many people want, he says.
"Tens of thousands of individuals contact us every year with questions about genital herpes, and about 40% of them have questions that relate specifically to testing," reports Ebel. "Often they feel they have been exposed to HSV by a sexual partner and simply want to know their status."
Blood tests for herpes can be used when a person has no visible symptoms but has concerns about having the infection. The tests do not actually detect the virus; instead, they look for antibodies in the blood.
Since 1999, there have been a number of new tests approved by the Food and Drug Administration to test for genital herpes, says Brown. These tests are very capable in separating antibodies due to the oral herpes virus from antibodies due to the genital variety.
According to ASHA, the following tests are type-specific:
- Biokit HSV-2 Rapid Test from Biokit USA, Cambridge, MA; also available as name Sure-Vue HSV-2 Rapid Test from Fisher HealthCare, Hamp-ton, NH.
- HerpeSelect HSV-1 and HSV-2 tests from Focus Diagnostics, Cyprus, CA.
- Herpes Western blot from University of Washington in Seattle.
- CAPTIA HSV IgG Type Specific ELISAs from Trinity Biotech USA, Berkeley Heights, NJ.
"The reason that the old serologic tests are still being sold has to do with the government’s inability to force the manufacturer to recall an outdated and inaccurate test," says Brown. "Currently, this will be accomplished only by market forces."
ASHA has published a Herpes Testing Toolkit that offers guidance to clinicians on which tests are FDA-approved as type-specific serologies and which clinical scenarios might call for these tests, says Ebel. As part of this effort, ASHA also publishes herpes patient counseling materials that are geared to the situation of serologic test results.
The latest science says the best answer to the question of "What is my status?" comes from type-specific serologic tests, he states.
"We are trying to increase awareness of this tool — among both clinicians and consumers," Ebel says.
References
- Morrow RA, Brown ZA. Common use of inaccurate antibody assays to identify infection status with herpes simplex virus type 2. Am J Obstet Gynecol 2005; 193:361-362.
- Centers for Disease Control and Prevention. Genital Herpes. CDC Fact Sheet. Accessed at: www.cdc.gov/std/ Herpes/STDFact-Herpes.htm.
Resources
For more information on herpes diagnostic tests, contact:
- Biokit USA, 113 Hartwell Ave. Lexington, MA 02421-3190. Telephone: (800) 926-3353 or (781) 861-4064. Fax: (781) 861-4065. Web: www.biokit.com.
- Fisher Scientific International, Liberty Lane, Hampton, NH 03842. Telephone: (800) 766-7000 or (603) 926-5911. Fax: (603) 929-2379. Web: www.fishersci.com.
- Focus Diagnostics, 10703 Progress Way, Cypress, CA 90630. Telephone: (800) 838-4548 or (714) 220-1900. Fax: (714) 220-1820. Web: www.herpeselect.com.
- Trinity Biotech USA, Four Connell Drive, Suite 7100, Berkeley Heights, NJ 07922. Telephone: (800) 325-3424. Fax: (908) 898-1063 or (908) 898-1085. E-mail: [email protected]. Web: www.trinitybiotech.com.
- University of Washington Virology Research Clinic, 600 Broadway, Suite 400, Seattle, WA 98122. Telephone: (206) 720-4340. Fax: (206) 720-4371. E-mail: [email protected]. Web: depts.washington.edu/herpes/.
The Herpes Testing Toolkit, published by the American Social Health Association (ASHA), is a 10-page guide with information on type-specific herpes serologic assays, clinical scenarios in which serologic testing may be beneficial, and key factors in a differential diagnosis for genital herpes. The toolkit contains pre- and post-testing fact sheets with key counseling messages for patients. To order, visit the ASHA web site, www.ashastd.org. Click on "Publications," "For Organizations," "STDs," and "Herpes Testing Toolkit." Prices are as follows: one to 19, $7.95 each; 20-49, $7.15 each; 50-99, $6.75 each; 51 or more, call for pricing. Shipping charges are $0-$49, $5; $50-$499, 9%; over $500, 7%. Orders may be placed on-line, or through the following contact information:
- ASHA Customer Service, P.O. Box 13827, Research Triangle Park, NC 27709. Telephone: (800) 783-9877. Fax: (919) 361-8430, Attention: Customer Service.
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