Diagnostic Testing for Genital and Oral Herpes
by Dr. H., Medical Director www.herpes.org
I am continuously asked by people through this website about testing for genital and oral herpes, as well as what the various tests mean regarding both oral and genital herpes. This paper will cover some of the essentials regarding testing for herpes infections.
The “gold standard” for diagnosis of herpes is the viral culture. If a viral culture taken at a clinic from an active herpes lesion is positive for herpes simplex, then this makes the diagnosis. The patient should always be sure to ask the doctor to perform complete typing of the virus so that the result will reveal if the virus in question is herpes simplex type 1 or type 2. This may be important later, especially regarding the possibility of transmission of the disease to others.
Sadly, the viral culture can be falsely negative for many reasons. The virus must survive the trip to the laboratory. Anything that may affect this survival negatively could then cause a false negative result. For example, if the sample became overheated, it could kill the virus and cause a false negative result.
A newer “gold standard” is even more sensitive than the viral culture. This test is called the PCR DNA test, and it can identify the DNA from viral particles to an extremely high degree of accuracy and can differentiate between the two types.1 This test directly reveals the presence of either type of virus from the lesion.
Wald et al showed in their 1997 paper that the PCR test was almost 300% more sensitive in picking up actual viral material from vaginal specimens than was the viral culture.2 Sadly, the PCR DNA test is not routinely available to the clinician in the office at this time.
Some so-called type-specific EIA tests which are reported as “type 2: type 1 ratios” are not truly type specific.3 Thus, a patient with an oral herpes simplex type 1 infection may show a false positive result for type 2 on some testing. The reverse may also be true. This scenario is the most common one that I hear on the website.
My recommendation on so-called type-specific EIA test blood work, which means any blood testing not discussed on these two pages, is not to do it. It is an unnecessary expense and may not offer results that can be trusted. A patient can be given a false sense of security about a test that is falsely negative OR the patient can be given a false anxiety about a test that is falsely positive.
Type Specific Blood Testing for Herpes Simplex
Recent developments in testing have been very helpful for type 2 herpes simplex. The POCkit test from www.diagnology.com is a highly type specific test for type 2 herpes simplex. It will detect antibody against herpes simplex type 2 and to an extremely high level of accuracy.4 This also means, though, that the test will not become positive until enough antibody shows up in the blood stream to be able to be detected. This could take as long as three months from the time of infection, but the mean time according to Wald et al in initial testing of this product was 13 days post exposure, though the variation was quite wide.4
The POCkit test is quick and easy to perform. It is available for the doctor to perform in the office, and its cost is reasonable. The POCkit test in fact tests for an antibody against a single viral protein.3
A similar and even more accurate, sensitive and type specific test is the Western Blot blood test. The Western Blot can distinguish between type 1 and type 2 herpes simplex antibody with extremely high accuracy approaching 99%.3 If this test is positive or negative for type 1, type 2, both, or neither viruses, then the patient can feel assured that at least the most accurate blood test available has been performed. The Western Blot tests for a wide profile of antibody respond against many herpes simplex virus proteins.3
Remember, in excess of 80% of humans in America have had exposure to oral, type 1 herpes simplex infections in the past. Thus, most people have antibody to type 1 HSV. Therefore, if a lesion is present that the doctor is CERTAIN is genital herpes AND the Western Blot shows only type 1, this would indicate that that lesion is type 1 herpes.
However, if a genital lesion that is uncertain to be herpes is found to be in association with a positive Western Blot for type 1, the Western Blot does not prove that that lesion is genital herpes because the virus has not been isolated from the lesion.
The Western Blot test has to be sent away to an outside laboratory and has a substantial turnaround time. The blood has to be appropriately drawn and protected during the sending of the blood to the laboratory.
The reader interested in obtaining the Western Blot blood test can contact either www.viridae.com or the Westover Heights Clinic at www.westoverheights.com for further information on obtaining these tests.
Dr. H’s Recommendations for Testing for Genital and Oral Herpes
First, the patient must see a doctor. The patient should try to find a physician that is knowledgeable in the diagnosis of genital and oral herpes and who will give the patient the time needed. If the patient does not know of a physician such as this in the area, the patient might ask a member of one of the support groups in that area.
Second, if an active, blistered lesion is present, ask for a viral culture for herpes simplex, and ask that the virus be typed (to distinguish between type 1 and type 2). If no active lesion is present, the viral culture may not be positive. Females that are having a vaginal discharge might have internal lesions that might be cultured. If the doctor has the ability to perform PCR DNA testing for herpes simplex, ask for that instead of a viral culture. The PCR DNA can find herpes simplex virus even when no symptoms are present.
Third, ask for the POCkit test for type 2 herpes simplex if the viral culture turns up negative, or wasn’t done because of no lesions being present. If the POCkit test is negative, and if symptoms continue to occur, then repeat the POCkit test ten weeks later IF the viral culture was negative (or wasn’t done). Remember, if the viral culture was taken AND was positive, then the diagnosis is made already.
Fourth, if symptoms keep occurring AND the viral culture and POCkit test were negative, then ask for the Western Blot test to be done. Remember, though, that positive type 1 antibody on the Western Blot does not prove that the lesion is type 1 herpes simplex unless the doctor is certain that the lesion is a herpes lesion.
I hope that this discussion may open some doors to the understanding of how testing for herpes simplex infections should be done. If a reader has further questions, drop me a line at the website.
1 Cullen, A. P., C. D. Long, and A. T. Lorincz. 1997. Rapid detection and typing of herpes simplex virus DNA clinical specimens by the hybrid capture II signal amplification probe test. J. Clin. Microbiol. 35:2275-2278
2 Wald A, Corey L, Cone R, Hobson A, Davis G, Zeh J 1997 Mar Frequent genital herpes simplex virus 2 shedding in immunocompetent women. Effect of acyclovir treatment. J Clin Invest 1;99(5):1092-7. Department of Medicine, University of Washington, Seattle 98195, USA. firstname.lastname@example.org
3 Nashat Nafouri, B.Sc., D.B., CLS 2001 Personal Communication; reference website www.viridae.com
4 Ashley RL, Wald A, Eagleton M Premarket evaluation of the POCkit HSV-2 type-specific serologic test in culture-documented cases of genital herpes simplex virus type 2. Sex Transm Dis 2000 May;27(5):266-9. Department of Laboratory Medicine, University of Washington, Seattle, USA.
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