Friday, August 17, 2007


I have "smoldering" myeloma (or just MGUS, depending how you look at it), which means my myeloma is not symptomatic. No broken bones, kidney failure, nothing. I even ran four marathons this year, so far.

But my numbers (IgG, M-Spike, Light Chains) keep climbing, so I walk around with my fingers crossed, hoping to continue smoldering but nervously looking for that first little flame somewhere.

Enter the CRAB criteria: Calcium, Renal (creatinine), Anemia (hemoglobin), and Bone lesions. A person is considered to have active myeloma ("end" organ damage) when any of these criteria are out of whack.

Mine seem to be well within whack, except for the first, calcium. In the last three lab tests, calcium has edged toward the high limit of normal according to that lab. So I checked the internet to see what is abnormal according to the CRAB criteria.

The first place I looked was the International Myeloma Foundation's page about CRAB. That got me more confused. So I called the hot line and Nancy Baxter called right back. Then we were both confused, so she put me on hold and called Dr. Durie! Good job, Nancy.

If I got it right, this is what he told her:
  • Normal calcium readings are right around 9 or 10 mg/dL (milligrams per deciliter), not mg/L (milligrams per liter) as is suggested in Table 1 of the IMF page about CRAB. One mystery solved, something for IMF to fix on their web page.
  • Perhaps the best CRAB limit for calcium is the local lab's own limit. Over that you've met one of the CRAB criteria.
  • However, calcium is not usually the first criteria of the four to be met; one of the others pops up first.
The implication of all of this is that I shouldn't be too worried yet, because my calcium is still (barely) below the limit. It could easily go down again, too, because it clearly does bounce around a bit. But I will be watching.

Here is a chart of my serum calcium since diagnosis. Looks like it's creeping up in the last six months:

Serum Calcium, click to enlarge, BACK to return here


  1. This is very interesting, Don. I was wondering if you take any vitamin D3. And if you do, do you think that might have influenced your calcium results? Anyway, thank you for this post, very helpful and informative, Margaret (my calcium levels are right smack in the middle of the normal range).

  2. Actually, now that you mention it, I have been taking a Vitamin D3 supplement (1000 IU) for a while now. I wonder if that time span would correlate with the time that my calcium has been a little higher than usual. I'm not sure I have records that will tell that tale.

    It's been a year since I had a bone density measurement; perhaps that would also tell a story. I'll ask the onc at next visit, three or four weeks from now.