B12 Binding Capacity (Unsaturated) Blood Test

[skiras1]

Hello - Our 11 year old son with a history of infections, high fevers, night terrors, and anxiety had a B12 Binding Capacity (Unsaturated) Blood Test three weeks ago and the results were low (537 pg/mL - the reference range is 800-2600 pg/mL). What should be our next steps? It was an immunologist that took the test and he told me to talk to our pediatrician (that is not knowledgeable at all on this subject).

[Gambit62 Administrator]

The low result suggests that there is a problem with producing one of the proteins that binds to B12 but doesn't actually identify which. Most likely it is a problem with TC2 which is the protein that allows the B12 to pass into cells so it can be used, but it could also be a problem with TC1 which helps B12 to actually get tot he point where it is absorbed in the gut.

Poor production of these proteins has genetic origins so it would probably be a good idea to see if you can get genetic tests done to see exactly which variant is causing the problem and hence which protein is being affected.

As I understand it treatment is likely to be B12 shots but I am not a medical expert.

[Gambit62 Administrator in reply to Gambit62]

you may also find this site useful if you are based in the US

b12awareness.org/

and there is a chapter on B12 in infants aimed at pediatricians in 'Could it be B12?' by Sally Pachalok et al.

[Frodo in reply to Gambit62]

Sorry to butt in here. Have never heard of this test before, is it a missing link in our testing process? Would it help when there is doubt in diagnosis due to serum levels being in normal range, do you think?

I see it's also useful for diagnosing myeloproliferative disorders which I was told my son had, then was told he didn't have - but he never had this test.

[Gambit62 Administrator in reply to Frodo]

Frodo this isn't a test I'd come across before either. It doesn't relate to B12 absorption problems - and unlikely that it is done outside paediatrics as anyone with the problems it identifies is likely to survive into adulthood. Doubt its available in the UK outside specialist units.