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Date of last update: 10/12/2017.

Forum Name: Viral Infections

Question: Positive Monospot Test but no IgM Antibodies??

 chaps - Fri Aug 29, 2008 4:34 am

I had a positive monospot test after complaining of glands up for several months. At the time I was scared of HIV and therefore a series of tests were done after 3 months to rule that out. My monospot flagged up positive twice in a row. Specific tests showed however that I had no IgM antibodies present, but IgG were present. My doctor said this was indicative of a past infection but could not confirm recent infection. My question is therefore, how can the monospot be positive if there are no IgM heterophile antibodies? All the info i read suggests that the monospot will be +ive only when there is a recent infection and IgM antibodies? My doctor wasn't sure and diagnosed it is a 'glandular fever type illness' following negative HIV, HCV and liver screening tests. I am unable to shift form my mind however that this was a false positive monospot and therefore one of the horrible and scary false-positive causes could be the problem. I am not ill currently but have frequent flare ups of glands - I have always been like this however and strongly suspect I have had mono in the past. The IgG would be present, but would this be a reason for a monospot test to show up positive? Please help put my mind at ease.
 John Kenyon, CNA - Sat Sep 20, 2008 9:15 pm

User avatar Hello -

It is very unlikely that a monospot test would come up false positive once, let alone twice. It is fairly unique and few other diseases (all within the Epstein-Barr family) can mimic it. There are additonal tests to confirm or refute the finding, but two consecutive positives would seem to seal the deal. The igG often doesn't show up anyway til later, when the infection is beginning to resolve. While you don't mention having had any specific symptoms of mono, there often are none (and those infected without symptoms are very fortunate), so that in no way indicates you don't have mono or one of its close relatives.

The test for mono is pretty specific and the positive finding is based on a unique blood cell morphology, so I think you can safely accept this diagnosis, especially since nothing else shows up to contradict it.

I hope this is helpful. Best of luck to you.

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