I am still relatively new to this forum and understanding the numbers. How do you calculate the M-spike just by the immunoglobulin levels, like Cheryl G did in this post? How do you know how many are the normal to subtract?
I learn so much by reading. Thanks in advance.
Eileen
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Eileenk - Name: Eileen
- Who do you know with myeloma?: me
- When were you/they diagnosed?: Smoldering, September 2017
- Age at diagnosis: 49
Re: Estimating M-spike from immunoglobulin results?
Hi Eileen,
As I mentioned in the post you referenced, for each reported immunoglobulin level (IgA, IgG, IgM, etc.), this equation is true:
Total immunoglobulin = Polyclonal (normal) immunoglobulin + Monoclonal immunoglobulin.
So for someone with IgG myeloma or MGUS,
Total IgG = Polyclonal IgG + Monoclonal IgG
or
Total IgG = Healthy IgG + M-spike
You can use the reference ranges for IgA, IgG, or IgM to give you an estimate of a patient's healthy IgG. Just take the middle of the range. For IgG, that would be about 1150 mg/dL. So if a patient's total IgG is reported to be 3820 mg/dL, a first-pass estimate of the M-spike would be (3820-1150) = 2670 mg/dL, or 2.67 g/dL given that 1000 mg = 1 g.
You may recall that my estimate wasn't 2.67 g/dL, but instead was around 3.0 g/dL. That's because I thought that in this particular case the "healthy IgG" might be lower than the midpoint of the normal range. I thought this because the patient's other immunoglobulins, IgA and IgM, were both below the normal range, so there seems to be some suppression of (healthy) immunoglobulin production going on.
If the healthy part of the 3820 mg/dL total IgG is lower than 1150 mg/dL, then the actual M-spike will be higher than 2670 mg/dL. I just guessed that the healthy IgG level might be around 800 or 850 mg/dL, which is why a estimated the M-spike might be around 3000 mg/dL (3.0 g/dL).
This can all seem rather complicated, not least because of the need to convert between milligrams and grams. The key thing to remember is that the total immunoglobulin results are always made up of two parts: healthy immunoglobulin and monoclonal immunoglobulin. If you know the total immunoglobulin level, just use an estimate of the healthy immunoglobulin level to give you an estimate of the M-spike.
As I mentioned in the post you referenced, for each reported immunoglobulin level (IgA, IgG, IgM, etc.), this equation is true:
Total immunoglobulin = Polyclonal (normal) immunoglobulin + Monoclonal immunoglobulin.
So for someone with IgG myeloma or MGUS,
Total IgG = Polyclonal IgG + Monoclonal IgG
or
Total IgG = Healthy IgG + M-spike
You can use the reference ranges for IgA, IgG, or IgM to give you an estimate of a patient's healthy IgG. Just take the middle of the range. For IgG, that would be about 1150 mg/dL. So if a patient's total IgG is reported to be 3820 mg/dL, a first-pass estimate of the M-spike would be (3820-1150) = 2670 mg/dL, or 2.67 g/dL given that 1000 mg = 1 g.
You may recall that my estimate wasn't 2.67 g/dL, but instead was around 3.0 g/dL. That's because I thought that in this particular case the "healthy IgG" might be lower than the midpoint of the normal range. I thought this because the patient's other immunoglobulins, IgA and IgM, were both below the normal range, so there seems to be some suppression of (healthy) immunoglobulin production going on.
If the healthy part of the 3820 mg/dL total IgG is lower than 1150 mg/dL, then the actual M-spike will be higher than 2670 mg/dL. I just guessed that the healthy IgG level might be around 800 or 850 mg/dL, which is why a estimated the M-spike might be around 3000 mg/dL (3.0 g/dL).
This can all seem rather complicated, not least because of the need to convert between milligrams and grams. The key thing to remember is that the total immunoglobulin results are always made up of two parts: healthy immunoglobulin and monoclonal immunoglobulin. If you know the total immunoglobulin level, just use an estimate of the healthy immunoglobulin level to give you an estimate of the M-spike.
Re: Estimating M-spike from immunoglobulin results?
Thank you, Cheryl! After reading your post, it makes complete sense to take a midpoint of the normal range, that just never occurred to me.
Have a great day.
Eileen
Have a great day.
Eileen
-
Eileenk - Name: Eileen
- Who do you know with myeloma?: me
- When were you/they diagnosed?: Smoldering, September 2017
- Age at diagnosis: 49
3 posts
• Page 1 of 1