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STDs (Expert Forum)
please help us understand
Answered by
University of Washington
Seattle - WA
Welcome to the STD Forum, which is intended only for questions and support pertaining to sexually transmitted diseases other than HIV/AIDS, including chlamydia, gonorrhea, syphilis, human papillomavirus, genital warts, trichomonas, other vaginal infections, nongonoccal urethritis (NGU), cervicitis, molluscum contagiosum, chancroid, and pelvic inflammatory disease (PID). All questions will be answered by H. Hunter Handsfield, M.D. or Edward W Hook, MD.
please help us understand
by notme2126, Jan 27, 2008 02:11PM
First of all, thank you all very much for starting a site like this. It is really nice to have a place where we can ask questions and feel certain that you all are providing us with honest answers! Anyway I'm very confused on why OBGYN offices have a numerical scale stating 1.1 positive and I have read on this site that the scale can range up to a 3. I have had 2 other test done, one saying no virus detected, and the other was equivocal which i had retested and it came back with a result of 1.7 the specific test I took as HSV type2 - specific AB, IGG and the reference range states 0.0- 0.8. Please explain why my doctors office believes me to be positive now, if the scale can actually range higher? Should I be tested AGAIN? please help me get out of the tug of war I'm having with this virus
Doctor's Answer
by H. Hunter Handsfield, M.D., Jan 27, 2008 03:52PM
, Jan 27, 2008 03:52PM
Thanks for re-posting your question here, not as follow-up in another thread. It addresses an important and confusing issue. This reply is complicated, so read it carefully. I'm constructing it not only for you and forum users, but as something that can be printed out and taken to a health care provider who isn't up to speed on it. Outside STD clinics and a few infectious diseases specialists, most providers do not understand these issues themselves.
First, more than one HSV blood test is on the market. The most common in the US is Focus Technologies' HerpeSelect test. If a lab uses Trinity Biotech's Captia HSV test, the numerical range of positive and negative results might be different. (Off the top of my head, I do not know the cut-off values for Captia.) Other tests are used elsewhere, such as the Kalon HSV test in the UK and probably other commonwealth countries. (The BiokitUSA HSV-2 test is also available in the US, but it doesn’t give a numerical result.) Further, some labs still use older, non-type specific HSV tests; those numbers are still different-- as well as the tests being inherently unreliable. The rest of the comments below relate only to the HerpeSelect HSV-2 test.
Second, as Dr. Hook said in the other thread, the understanding of what numbers should be considered positive are changing. Many specialists now understand that although HSV-2 EIA ratios of 1.1 to 3.5 are technically positive, many are falsely positive. (Some researchers use a cut-off of 3.0 instead of 3.5, yet another wrinkle.)
Third, HSV-1 might affect the HerpeSelect HSV-2 result. A single study suggests that false positive HSV-2 results (in the range of 1.1 to 3.5) occur mostly in people with positive HSV-1 results. I stress "suggests": even though I was one of the researchers on that study, it is rare that a single study should be interpreted as solid truth. Still, some providers are using that information in how they inform their patients, and I have done so at times on this forum.
In the US, each manufacturer, and every lab using a particular manufacturer's test, by law must interpret the results according to the data available when FDA approved the test for marketing. That is true even when new data come along that show better numbers, unless and until the manufacturer assembles a revised application to the FDA--an expensive, time-consuming process, therefore not done frequently. For now, Focus officially considers the HerpeSelect HSV-2 result to be negative if the EIA ratio is 0.9 or lower, equivocal at 0.9 to 1.1, and positive if above 1.1. With rare exception, that is how labs report the results to doctors' offices. However, as suggested above, some providers might not use exactly those numbers as the basis of what they tell their patients.
Another minor point that might be pertinent to your own test result: According to what I just said, a result of 0.89 is negative. But a particular lab might round things off. Since 0.9 to 1.1 is equivocal, perhaps your lab--in an attempt to keep thing simple--defines 0 to 0.8 as negative, instead of 0 to 0.89. This might explain why they state the "reference range" as 0 to 0.8.
And yet another issue (I told you this is complicated!): The proper interpretation of any laboratory test, whether for herpes or anything else, depends on clinical context. If someone is highly likely to have HSV-2 (e.g., the regular partner of a known-infected person, or recurrent symptoms typical of genital herpes), even an equivocal result usually is considered positive. In someone at very low risk-- the worried well who shouldn't have been tested anyway, whose symptoms don't suggest herpes, etc--even a fairly strongly positive result should be interpreted with caution, and most equivocal low-positive should be interpreted with great care, knowing they may be false. Wise clinicians and wise patients generally do not interpret a single test result, all by itself, as definitive proof for or against a particular diagnosis.
A final point of principle: ALL the tests we have been talking about are IgG tests. ONLY type-specific IgG testing is valid in testing for HSV. IgM results ALWAYS are unreliable: many (most?) positive results are false, no IgM test is type specific. Even though many labs do IgM HSV tests routinely (they are cheap money-makers), in adults the results NEVER MAKE A DIFFERENCE AND ALWAYS SHOULD BE IGNORED. Pardon the all-capitals “shout”, but I cannot stress this too strongly.
So what to do? First, most patients should just rely on their providers' interpretation of the test, and not get hung up on the numbers. Those numbers should be viewed as communication from lab to doc, not intended to be given to patients themselves. Of course, this can be a problem if the doc isn't up to speed on these issues. Second, always disregard IgM results, no matter what they show.
Third, for the HSV-2 HerpeSelect, here are what the EIA ratio results normally mean:
0 to 0.89: Definitely negative. It someone has two results of say 0.4 and 0.8, there is no difference between them. Both results are absolutely negative. There is no such thing as "a little bit" of HSV-2 antibody that changes the result, as long as it's below 0.9.
0.90 - 1.10: Equivocal; cannot say anthing one way or another. Most such people probably do not have HSV-2, but some may. Repeat testing usually will sort it out.
1.11 to 3.49: Usually positive, but with risk that some results are falsely positive. A false positive result might be especially likely if the HSV-1 test result also is positive. With results in this range, it is particularly important to interpret the result in the context of the prior likelihood someone has genital herpes. If I have a patient with a story of recurrent genital symptoms that sound like herpes, and s/he has a HSV-2 HerpeSelect result in this range, I tell him or her that the result is positive and confirms what was already suspected: s/he has genital herpes. If I have someone who is HSV-1 positive and neither the symptoms nor exposure history suggests herpes, I tell them the result is equivocal; we'll either have to wait and see, or repeat testing might be done.
3.5 and up: Positive for HSV-2; the person has genital (or genital area) herpes. But there might be rare exceptions even here. Repeat testing might be necessary if there are strong reasons to doubt the diagnosis.
Whew! Sorry to provide a lot more information than you wanted. But now I have an FAQ response that I can refer other questioners to in the future. I’ll bet this thread gets a lot of reading in coming months and years.
Finally, I haven't forgotten your specific concerns. If other evidence strongly supports the idea that you have genital herpes, your result should be considered positive. If nothing else supports herpes--no contact with an infected partner, no symptoms of herpes--it is likely that your result is falsely positive. If in doubt, ask your provider for a repeat test; and if that is in the same range, have the specimen sent to the University of Washington lab for a Western blot test. That's the final, tie-breaking gold standard for HSV antibody testing.
Best regards-- HHH, MD
First, more than one HSV blood test is on the market. The most common in the US is Focus Technologies' HerpeSelect test. If a lab uses Trinity Biotech's Captia HSV test, the numerical range of positive and negative results might be different. (Off the top of my head, I do not know the cut-off values for Captia.) Other tests are used elsewhere, such as the Kalon HSV test in the UK and probably other commonwealth countries. (The BiokitUSA HSV-2 test is also available in the US, but it doesn’t give a numerical result.) Further, some labs still use older, non-type specific HSV tests; those numbers are still different-- as well as the tests being inherently unreliable. The rest of the comments below relate only to the HerpeSelect HSV-2 test.
Second, as Dr. Hook said in the other thread, the understanding of what numbers should be considered positive are changing. Many specialists now understand that although HSV-2 EIA ratios of 1.1 to 3.5 are technically positive, many are falsely positive. (Some researchers use a cut-off of 3.0 instead of 3.5, yet another wrinkle.)
Third, HSV-1 might affect the HerpeSelect HSV-2 result. A single study suggests that false positive HSV-2 results (in the range of 1.1 to 3.5) occur mostly in people with positive HSV-1 results. I stress "suggests": even though I was one of the researchers on that study, it is rare that a single study should be interpreted as solid truth. Still, some providers are using that information in how they inform their patients, and I have done so at times on this forum.
In the US, each manufacturer, and every lab using a particular manufacturer's test, by law must interpret the results according to the data available when FDA approved the test for marketing. That is true even when new data come along that show better numbers, unless and until the manufacturer assembles a revised application to the FDA--an expensive, time-consuming process, therefore not done frequently. For now, Focus officially considers the HerpeSelect HSV-2 result to be negative if the EIA ratio is 0.9 or lower, equivocal at 0.9 to 1.1, and positive if above 1.1. With rare exception, that is how labs report the results to doctors' offices. However, as suggested above, some providers might not use exactly those numbers as the basis of what they tell their patients.
Another minor point that might be pertinent to your own test result: According to what I just said, a result of 0.89 is negative. But a particular lab might round things off. Since 0.9 to 1.1 is equivocal, perhaps your lab--in an attempt to keep thing simple--defines 0 to 0.8 as negative, instead of 0 to 0.89. This might explain why they state the "reference range" as 0 to 0.8.
And yet another issue (I told you this is complicated!): The proper interpretation of any laboratory test, whether for herpes or anything else, depends on clinical context. If someone is highly likely to have HSV-2 (e.g., the regular partner of a known-infected person, or recurrent symptoms typical of genital herpes), even an equivocal result usually is considered positive. In someone at very low risk-- the worried well who shouldn't have been tested anyway, whose symptoms don't suggest herpes, etc--even a fairly strongly positive result should be interpreted with caution, and most equivocal low-positive should be interpreted with great care, knowing they may be false. Wise clinicians and wise patients generally do not interpret a single test result, all by itself, as definitive proof for or against a particular diagnosis.
A final point of principle: ALL the tests we have been talking about are IgG tests. ONLY type-specific IgG testing is valid in testing for HSV. IgM results ALWAYS are unreliable: many (most?) positive results are false, no IgM test is type specific. Even though many labs do IgM HSV tests routinely (they are cheap money-makers), in adults the results NEVER MAKE A DIFFERENCE AND ALWAYS SHOULD BE IGNORED. Pardon the all-capitals “shout”, but I cannot stress this too strongly.
So what to do? First, most patients should just rely on their providers' interpretation of the test, and not get hung up on the numbers. Those numbers should be viewed as communication from lab to doc, not intended to be given to patients themselves. Of course, this can be a problem if the doc isn't up to speed on these issues. Second, always disregard IgM results, no matter what they show.
Third, for the HSV-2 HerpeSelect, here are what the EIA ratio results normally mean:
0 to 0.89: Definitely negative. It someone has two results of say 0.4 and 0.8, there is no difference between them. Both results are absolutely negative. There is no such thing as "a little bit" of HSV-2 antibody that changes the result, as long as it's below 0.9.
0.90 - 1.10: Equivocal; cannot say anthing one way or another. Most such people probably do not have HSV-2, but some may. Repeat testing usually will sort it out.
1.11 to 3.49: Usually positive, but with risk that some results are falsely positive. A false positive result might be especially likely if the HSV-1 test result also is positive. With results in this range, it is particularly important to interpret the result in the context of the prior likelihood someone has genital herpes. If I have a patient with a story of recurrent genital symptoms that sound like herpes, and s/he has a HSV-2 HerpeSelect result in this range, I tell him or her that the result is positive and confirms what was already suspected: s/he has genital herpes. If I have someone who is HSV-1 positive and neither the symptoms nor exposure history suggests herpes, I tell them the result is equivocal; we'll either have to wait and see, or repeat testing might be done.
3.5 and up: Positive for HSV-2; the person has genital (or genital area) herpes. But there might be rare exceptions even here. Repeat testing might be necessary if there are strong reasons to doubt the diagnosis.
Whew! Sorry to provide a lot more information than you wanted. But now I have an FAQ response that I can refer other questioners to in the future. I’ll bet this thread gets a lot of reading in coming months and years.
Finally, I haven't forgotten your specific concerns. If other evidence strongly supports the idea that you have genital herpes, your result should be considered positive. If nothing else supports herpes--no contact with an infected partner, no symptoms of herpes--it is likely that your result is falsely positive. If in doubt, ask your provider for a repeat test; and if that is in the same range, have the specimen sent to the University of Washington lab for a Western blot test. That's the final, tie-breaking gold standard for HSV antibody testing.
Best regards-- HHH, MD
