What is the difference between IgM and IgG blood tests?

[Serpere]

I've been reading up on different blood test types. I keep coming across IgM and IgG, but also have heard about Nucleic Acid Amplification Testing (NAAT) . I would like to know what the difference is between these types of blood tests. What are the main practical differences between the types of testing, the benefits/costs of each?

I've come across different suggestions and I am trying to find the most reliable tests. Here is one turned me off of IgM

"IgM tests are not recommended because of three serious problems:

• Many assume that if a test discovers IgM, they have recently acquired herpes. However, research shows that IgM can reappear in blood tests in up to a third of people during recurrences, while it will be negative in up to half of persons who recently acquired herpes but have culture-document first episodes. Therefore, IgM tests can lead to deceptive test results, as well as false assumptions about how and when a person actually acquired HSV. For this reason, we do not recommend using blood tests as a way to determine how long a person has had herpes. Unfortunately, most people who are diagnosed will not be able to determine how long they have had the infection.
• In addition, IgM tests cannot accurately distinguish between HSV-1 and HSV-2 antibodies, and thus very easily provide a false positive result for HSV-2. This is important in that most of the adult population in the U.S. already has antibodies to HSV-1, the primary cause of oral herpes. A person who only has HSV-1 may receive a false positive for HSV-2.
• IgM tests sometimes cross-react with other viruses in the same family, such as varicella zoster virus (VZV) which causes chickenpox or cytomegalovirus (CMV) which causes mono, meaning that positive results may be misleading."

What are you experiences here? The details of this analysis go over my head but does anyone know whether the general summary is correct: that IgM tests are worst than IgG tests?

 

 

[mr_hopp]

Yes, IgM tests basically don't give reliable results. IgG are better as far as being accurate. The gold standard is the Western Blot. 

[sarahsfocus]

how does the western blot work? I have heard about it but it has never been explained to me.

 

[mr_hopp]

Here’s a quick write up on that:

http://depts.washington.edu/rspvirus/documents/hsv_western_blot.pdf

[sarahsfocus]

thanks.my sister wants me to take a herpes test.i wonder which one is the most Accurate? to be honest I'm terrified.

[mr_hopp]

They are most accurate in the order I listed them: IgM (least accurate), IgG (more accurate), Western Blot (most accurate)

[sarahsfocus]

ok so I took the IgG yesterday.the doctor told me they can distinguish between hsv1 and hsv2. I just pray I'm negative.

[mr_hopp]

They technically can give you results, but IgG test also have been known to give both false positives and false negatives. 😕 

[sarahsfocus]

I hought the IGg was really accurate.the health dept in my home town still uses the igM test. i'm glad I didn't go there.i still hope i'm negative.