Why B12 levels instead of Methylmalonic acid?

[Faebinder]

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So how come on most inpatient psych floors we check Vit B12 levels instead of the methylmalonic acid? Clearly methylmalonic acid is more sensitive for Vit b12 deficiency. Even Mass General book recommends Vit B12 and does not mention Methylmalonic acid. On the other hand, primary care screens with Methylmalonic acid.

 

[Shalom77]

On the other hand, primary care screens with Methylmalonic acid.

Not everywhere. I still see Vit B12 checked as a screen. I don't think there's a consensus. (However if there is and I'm ignorant please show me where to find it. 🙂 )

Seems like a common algorithm is to check vitamin b12 levels and then if indicated go on to check methylmalonic acid.

I think one of the issues with methylmalonic acid determination is cost - it's a much more expensive test.

This is an older article, but Fig 4 shows an algorithm.

http://archinte.ama-assn.org/cgi/reprint/159/12/1289

 

[michaelrack]

thanks for the great reference!

I usually start off with a B12 level. If it's low I treat for B12 deficiency. If it is at the low end of nl, I check an MMA. I don't check homocysteine or do the Schilling test.

I initially treat B12 deficiency with IM therapy, but sometimes will try switching to high dose oral therapy (1000 mcg daily) with close monitoring of B12 blood levels.

Although I usually check folate when I check B12, I don't think I've ever seen a folate level come back low.

 

[Faebinder]

thanks for the great reference!

I usually start off with a B12 level. If it's low I treat for B12 deficiency. If it is at the low end of nl, I check an MMA. I don't check homocysteine or do the Schilling test.

I initially treat B12 deficiency with IM therapy, but sometimes will try switching to high dose oral therapy (1000 mcg daily) with close monitoring of B12 blood levels.

Although I usually check folate when I check B12, I don't think I've ever seen a folate level come back low.

That makes a lot of sense. I'll start doing that.