Are antibody tests just measuring the level of the antibody response from the immune system?

[Gingergrrl]

NB: This post was split from this thread.

All antibody titer tests do not detect the virus itself, but measure the level of antibody response from the immune system.

@Hip and @Jonathan Edwards This issue still confuses me, and I apologize as I know I have asked about it before!

Do you mean that all antibody tests (whether a test from Quest for EBV, or a test from ARUP measuring enteroviruses, or a test from Mayo or Stanford measuring Virus XYZ, etc) are just measuring the level of the antibody response from the immune system?

If someone was autoimmune, could their body give a higher response to viruses that they have been exposed to in the past but it does not mean that the virus is currently active?

Does this also apply to the level of an autoantibody titer (or do those always measure someone's *current* level vs. a past one)? For example, when my Endo tests me every three months for the two Hashi's auto-abs, or any of my other auto-antibodies (calcium channel, GAD65, etc) those are actually capturing that moment in time (not a past exposure to something)?

Is this correct or am I totally off?

 

[Jonathan Edwards]

@Hip and @Jonathan Edwards This issue still confuses me, and I apologize as I know I have asked about it before!

Do you mean that all antibody tests (whether a test from Quest for EBV, or a test from ARUP measuring enteroviruses, or a test from Mayo or Stanford measuring Virus XYZ, etc) are just measuring the level of the antibody response from the immune system?

If someone was autoimmune, could their body give a higher response to viruses that they have been exposed to in the past but it does not mean that the virus is currently active?

Does this also apply to the level of an autoantibody titer (or do those always measure someone's *current* level vs. a past one)? For example, when my Endo tests me every three months for the two Hashi's auto-abs, or any of my other auto-antibodies (calcium channel, GAD65, etc) those are actually capturing that moment in time (not a past exposure to something)?

Is this correct or am I totally off?

There are all sorts of ways things can interfere. With rheumatoid factor autoantibodies present all titres of other antibodies can appear artifactual higher.

There is also an anamnestic response in which antibodies to everything may go up when you respond to something else for a while.

The problem is that it is all so unpredictable that you cannot conclude much from high levels of antibodies to microbes except that you have probably met the microbe some time in the past. In general high antibody levels to viruses mean nothing much. Some people produce antibodies that show up very high on assays and others produce antibodies that score lower, and they may change over time, but it means very little. The only thing that really means much is if you have a blood test at the time of an illness and then later and your antibody goes from none to positive then that acute illness was probably the first time you met the microbe. It is useful in acute infectious disease work but pretty useless for chronic illness.

 

[Gingergrrl]

There are all sorts of ways things can interfere. With rheumatoid factor autoantibodies present all titres of other antibodies can appear artifactual higher.

@Jonathan Edwards Would this only be the case re: rheumatoid factor auto-abs or could other auto-abs also make viral titers present as artificially higher?

The only thing that really means much is if you have a blood test at the time of an illness and then later and your antibody goes from none to positive then that acute illness was probably the first time you met the microbe. It is useful in acute infectious disease work but pretty useless for chronic illness.

This makes sense and all my life I was completely negative for EBV on IgM and IgG (don't know how I avoided it) until age 41 when I actually got severe mono and then the IgM changed to positive. Then for 3-4 years after that the IgM, IgG, EA, etc, all stayed positive but am now thinking this was a "red herring" and didn't mean much except that my immune system was shifting into chaos.

Rituximab for lymphoma innerly always given together with drugs that have a much more potent immunosuppressive effect - hitting innate as well as adaptive immune responses. Opportunistic infections are therefore quite common in the context of rituximab but that is a long way from saying that rituximab is a major factor, or even relevant.

This is what I am hearing as well. I've asked the nurses at the infusion center where I get my IVIG about RTX (b/c it is a cancer center) and many cancer patients get a regime called "CHOP" of (cyclophosphamide, doxorubicin, vincristine, and prednisone) or some get "CHOP-R" plus the monoclonal antibody Rituximab. And even those patients do not get PML or life threatening infections. But if they did, it would be hard to say it was from the RTX vs. the other chemos.

As a rule rituximab does not reduce antibody levels to pathogens in people with autoimmune disease. My lab has hundreds of measurements indicating that.

That is very good to hear and is also my understanding (that RTX alone for autoimmune issues does not reduce antibody levels to dangerous pathogens in most cases).