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IgM Combination Test

Dr. H,
I have read your montra to ignore IgM tests, but today I received HSV results that were as follows:

(The tests were run at Lapcorp)
HSV, IgM I/I Combination 1.03 Equivocal
HSV, I/II, IgG/Rfx Type II IgG <0.9

I was tested with my prior girfriend and found to be negative for both HSV I & II several years ago. No other partners since. I have had no symptoms, but have been dating a woman who just found out her IgG Type I and II are positive (both >4). She reports no history of genital symptoms, but was aware that she has Type I coldsores about 1x year.

My Dr. wants to repeat my bloodwork in 60 days.

Should I be concerned? Are there other reasons other than HSV antibodies that the IgM Combination test would be measuring?
5 Responses
239123 tn?1267651214
The mantra is unchanged.  Your IgM result is meaningless.  There is a group of herpes specialists (I am one of them) in the process of writing letters to try to convince LabCorp, Quest, and the other major laboratories from even doing such tests.  False positive results are extremely common--probably not due to cross reaction with some other infection, just related to the biology and chemistry of the IgM molecule.

As the partner of someone with genital herpes (HSV-2, whether or not your partner is symptomatic), you are at high risk of infection.  But the type-specific IgG tests are the only ones that will reliably indicate whether or not that has happened.

Best wishes--  HHH, MD
Avatar universal
Here are some older posts concerning the IgM test:

LabCorp's default test is a non type specific IgG test.  If this test returns positve, you'll then be tested with the HerpeSelect ELISA for  hsv2.  If the hsv2 test is negative, then it's assumed you're hsv1 positive, and no further testing is done.  If the hsv2 test is positive, you're then tested with the HerpeSelect ELISA for hsv1.  (Source: LabCorp web site)  Personally, it find this a waste of time/money, since the wholesale price of a HerpeSelect test types is about 20-25 Dollars.

Labcorp does offer the HerpeSelect test, but it needs to be requested.

Your IgM should be tossed, and you're IgG is negative.
Avatar universal
Thank you for writing Labcorp concerning IGM.  This is much
abused by some STD Clinics or "Test sites" who inform patients they have had an recent exposure; and of course, inform the paniced patent they need further testing which can result in an "endless loop" of testing (IGM Positive, IGG negative) at considerable cost to the patient and of course profit to the
Avatar universal
Thank you all for the very helpful information!!  I understand the theory behind doing a IgM test if exposure has been recent and not enough time has passed for IgG antibodies to develop; however, as suggested by Dr. H and others, the test is highly prone to false positives. I hope this is true in my case.
239123 tn?1267651214
False positives indeed are a major problem, but HSV IgM antibody testing doesn't work in the way intended anyway.  In general IgM antibody precedes IgG for many infections, but it often isn't true for HSV; i.e., absence of IgM doesn't necessarily mean the infection is longstanding.  In addition, there is some (admittedly soft) information that IgM antibody sometimes is produced in response to symptomatic herpes recurrences, so a positive IgM test does not necessarily indicate recent infection.  In other words, HSV IgM testing just doesn't work the way docs (and lab directors) think it does.

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