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Tuesday, October 11, 2011

More on M Spike and IgA levels

Well, we now appear to have an embarrassment of riches, going from no email notifications to sending out three full posts at a time.  I'm still working on this.  My objective is to simply notify the email followers that a new post has been added, so they can go to the blog website to read it.  I'll fiddle with the settings tonight and see how it works out tomorrow.  Stay tuned.

Today was my infusion day at DFCI.  All went well.  The blood test results looked pretty good, although the anemia numbers (RBC, HGB, HCT) got a little worse compared to last week.  I'm getting kind of used to this weekly trip into Boston.  Since my appointments are usually in the afternoon, the trip in is a breeze, but I do have to fight rush hour traffic coming back home.  Most of my time at the clinic is spent just waiting.  First I get a blood draw.  Then I have to wait about two hours for the results to come back.  Then I can take the MLN 9708 drug, along with my Revlimid that I bring from home, and then I have to wait another hour before getting the dexamethasone.  My nurse, Heather, and I both think it's kind of ridiculous for me to just sit there and wait that last hour.  Why can't they just give me the dex up front and trust me to take it on time?  After all, they trust me with the Rev.  Heather and I are conspiring to find a way around this.  Besides, that would help me to miss the Boston rush hour traffic on the way home.

I've done a little more research on interpreting the M Spike from the Serum Protein Electrophoresis Test (SPEP) and the total immunoglobulin type and level from the Serum Immunofixation test.  The SPEP test is a simple screening procedure that identifies the presence of a likely monoclonal protein and gives an approximate estimate of the magnitude of the M Spike.  To validate that the spike is indeed monoclonal, the immunofixation test is then performed using monospecific antibodies.  Immunofixation is more sensitive than SPEP, and also determines the specific heavy chain and light chain components of the monoclonal protein (IgA Kappa in my case).  However, unlike SPEP, immunofixation doesn't estimate the size of the M protein, as it includes the level of polyconal protein as well.

I have argued previously that subtracting the M Spike level from the total immunoglobulin level theoretically should give an estimate of the normal polyclonal immunoglobulin level.  However, both tests are subject to errors of different types, so that this comparison is not done in practice.  Besides, such an estimate of the polyclonal protein level is not particularly useful.  What is important is: Is there an M Spike, and what kind is it?

The bottom line is that once the presence of the monoclonal protein has been established via immunofixation, this test doesn't need to be performed again during treatment unless needed to document a Complete Response (CR) to therapy.  Patients can be followed using only the M Spike level from the SPEP test.  If the M Spike disappears, a negative imunofixation result validates that there is no detectable monoclonal protein.  That, coupled with a bone marrow test showing less than 5% plasma in the marrow, is sufficient to validate a CR.  Of course, this is what I am hoping for from my therapy over the next few cycles.

I think this horse died a while ago and I am continuing to beat it, so I will refrain from boring you any further on this topic.  I can already hear your sighs of relief.

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