Likelihood of being a bone marrow donor match?

Contemplating joining the National Bone Marrow Donor Program.

In their FAQ, one of the question is If I join the Be The Match Registry, how likely is it that I will donate to someone?

Their answer is “We cannot predict the likelihood because there is so much diversity in the population.” This is a bullshit copout. Not that it will particularly affect my decision to sign up or not, but does anyone know how many people are in the registry, and how many are identified as a match (and called upon to donate) in any given calendar year?

How can they possibly predict the likelihood of your particular genetic background being a match for another’s without first typing it? You could be a common match, or a rare anomaly. Any overall statistics would be meaningless.

No more meaningless than defining the likelihood of developing breast cancer, or MS, or any other probabilistic event in a large population.

The simplest definition (which is all I’m looking fo) is the number of matches per year divided by the number of donor registrants on the list. For example, if there are a million registered donor candidates on the list, and a thousand people are matched (and called upon to actually donate marrow) in one year, then in the absence of any more specific information, any registrant’s probability of becoming an actual donor is 0.1%. I don’t think this is a meaningless statistic.

Looks like the information you need is here, but I don’t have time to dig for it. Have fun.

I wouldn’t say it would be “meaningless” if people are just trying to get an idea of what they can likely expect. For example, if 95% of potential donors get a call about a match you might want to think more about how you’ll handle the call than if only 0.000000001% do. Sure, it doesn’t change whether or not you specifically will be a match, but some people might want to know what a typical likelihood may be.

I recently signed up, and wondered the same thing - might I be called 20 times to be a donor, or is it unlikely I will ever get the call?

I did it for a little boy named Justin who turned 1 a few months ago and has Leukemia. Unfortunately (yet not surprisingly) I wasn’t a match for him. Hopefully somebody else out there will be. If you’re reading this thread, I urge you to sign up for the registry. They just do a cheek swab to get you on the list, and if you ever are called to donate, it’s usually an outpatient procedure. A small price to pay to give a someone like this sweet little boy a chance to grow up.

And to answer the OP’s question a little better, from what I can find it looks like 15,000-20,000 bone marrow transplants occur in the U.S. annually. The National Bone Marrow Registry claims over 8 million individuals, so that would work out to about 0.25% of potential donors donating in a given year. If we were to assume the average donor is on the list for 20 years, that would be about a 5% chance of donating.

Obviously these numbers may be very skewed, but they can probably give you a ballpark idea. So I’d probably guess that the likelihood is somewhere around, “fairly small, but far from astronomically so”

Keep in mind, my numbers don’t account for:

  • If that 15,000-20,000 includes donations from family members or not.
  • For every donation, there may actually be many potential matches that get the call, but only one of them is chosen as “the best match”
  • Probably a lot of other stuff that I haven’t considered

Wouldn’t it depend a great deal on your specific tissue type? My daughter is signed up as a bone marrow donor. She is type AB+, so IMHO it is unlikely she’ll ever be asked, since she could only donate to an AB+ recipient, without even starting to look at other tissue characteristics.

I am also AB+. I have been on the Marrow Donor Registry for 13 years now and I’ve not heard a peep from them. Maybe they could figure the likelihood of the most common matches but for I don’t see how that would apply to people with less common types. As much as I’d love to be able to donate, I went into it with the knowledge that it’s unlikely that I ever will. Hell, I can’t even donate to my immediate family members so what chance do I have of donating to a complete stranger?

Blood type doesn’t matter. Well, it can influence the way the bone marrow is processed, but it’s not how compatibility is judged.

When a bone marrow (or peripheral blood stem cell or cord blood) transplant seems the best treatment regimen, the patient’s immediate family is typed first. If no match is found, computer searches are done against the various registries. Non-white donors are urgently needed; this chart shows why & is relevant to the OP’s question. The searches don’t go by racial or ethnic characteristics, but the HLA markers tend to match within those groups.

I’m AB+ as well. I once got a letter about being a potential match, and more blood was taken for further type testing. It turned out I wasn’t a good enough match.

So when they took my blood all those years ago, and they typed me for the blood/platelet donations and the Marrow registry, they were typing for 2 different things?

So, does this mean that an AB+ person could donate marrow to an O- person if they had enough HLA markers that matched?

I’m so confused. Ya think you understand something and then someone throws a whammy at you. :stuck_out_tongue:


Wow! That’s weird/cool!

That IS very cool. I love learning new stuff. I thought I had read that fact/myth thing before. Hmm, I must be losing my memory.

The thing is, the pool of donors does not match the general population. For example, white people are way overrepresented in the donor pool, so if you’re, say, half black and half Pacific islander you might be a lot more likely to get matched to somebody because there just aren’t enough people on the registry with those genetic characteristics.

I don’t understand. Wouldn’t you be much less likely to be a match in that case?

I think he’s saying that since minorities are underrepresented in the donor registry (but don’t necessary have less of a need for donations), they’d be more likely to call you if you’re “close enough” rather than a perfect match.

Sort of like how an ugly woman would be much more likely to find a date on an aircraft carrier than in L.A. A smaller pool of options makes you more desirable.

Let’s say that you’re in an ethnicity that has a lot of people in the registry (whites, essentially.) There’s a chance that you could match someone needing a transplant, but maybe ten other people also match because there are so many people on the list, and they are all closer to the recipient, so you don’t get called to donate.

But if there are 1/10th the amount of people on the list, then you might be the only match, so they’ll probably ask you to donate.

Now, I’m sure for some ethnicities there are also less people needing the transplant, but from what I understand it’s not an equivalent ratio for donors. There might be three times as many total white people getting leukemia as blacks, but there might also be ten times as many whites on the registry, so it still works out that a black donor is more likely to be needed. (Not real numbers, just used as an example.)

Ah. Understood. Thank you.