If the center the patient goes to changes the m-protein estimating process (i.e., changes from sending the blood draw to an outside reference lab to processing the blood sample in an in-house lab), can this explain a different result than expected?
For example, the patient went from 0.3 each month for 1 year to 0.6 in one month, with all other proteins (i.e., IgG, kappa/lambda ratio, etc.) being the same.
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Re: Can a change in labs change M-spike levels?
We recently had a similar question, and I will share the answer we got from a very good doc.. There is a "valid" measurement error of 0.1 g/dL (1 g/L), from reader to reader of the test.
At 0.2, it's still possible that it's the exact same result, just read the same, but starting to get less plausible, and less so at 0.3. I have frequently heard that doctors report differences in test labs, though. If you had the exact same reading, it would suggest that one of the two test labs is better than the other. So it's not 100% sure, so you need to watch the trends going forward. If you stay at 0.6 for a long time, it might be just the change of the lab.
In any case, another variable is what is a relapse. I have read differences in that as well, but the smallest increase that I have seen that people treat is 0.5, which you are still under. The IMWG has a much laxer definition of a relapse, however, which is an increase of 1 in the M-spike.
At 0.2, it's still possible that it's the exact same result, just read the same, but starting to get less plausible, and less so at 0.3. I have frequently heard that doctors report differences in test labs, though. If you had the exact same reading, it would suggest that one of the two test labs is better than the other. So it's not 100% sure, so you need to watch the trends going forward. If you stay at 0.6 for a long time, it might be just the change of the lab.
In any case, another variable is what is a relapse. I have read differences in that as well, but the smallest increase that I have seen that people treat is 0.5, which you are still under. The IMWG has a much laxer definition of a relapse, however, which is an increase of 1 in the M-spike.
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JPC - Name: JPC
Re: Can a change in labs change M-spike levels?
Changes in M-spike can drive anyone crazy, especially changes due to the use of different labs.
As already has been mentioned, M-spikes can vary from different labs. Also, depending on your myeloma isotype (IgG, IgA, IgM, etc.), variations can be more apt to happen - at least in my experience. Specifically IgA, because this protein travels in the beta peak on the serum protein electophoresis (SPEP), and therefore is sometimes not completely assessed by SPEP if the assessment is made by looking only at the gamma peak, where most antibodies are found.
I would try to be patient and have the M-spike repeated at the same lab, if possible, to see what is going on.
Hopefully, the 0.3 is just a difference due to the change in the labs.
As already has been mentioned, M-spikes can vary from different labs. Also, depending on your myeloma isotype (IgG, IgA, IgM, etc.), variations can be more apt to happen - at least in my experience. Specifically IgA, because this protein travels in the beta peak on the serum protein electophoresis (SPEP), and therefore is sometimes not completely assessed by SPEP if the assessment is made by looking only at the gamma peak, where most antibodies are found.
I would try to be patient and have the M-spike repeated at the same lab, if possible, to see what is going on.
Hopefully, the 0.3 is just a difference due to the change in the labs.
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Dr. Ken Shain - Name: Ken Shain, M.D., Ph.D.
Beacon Medical Advisor
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