Positive GPC but Normal B12

[Cathyjw]

Hello,

I've just found out that my GPC test came back positive but my IFAb came back negative. My last b12 result was 284 (130-800) but I had been self supplementing prior to this. When I wasn't self supplementing my b12 was as low as 149. I've now paid to have active b12 checked privately along with a repeat b12 test but haven't had these taken yet. I have so many symptoms of deficiency but I'm concerned my gp won't treat me while my b12 is within their normal range. Has anyone else been treated with a normal level but positive GPC?

[fbirder]

GPC antibody test is no longer reccomended because it can give false positives.

The symptoms of B12 deficiency are similar to those of many other conditions. Are you sure yours aren't caused by one of them?

[Cathyjw in reply to fbirder]

No im not sure because how can you ever be sure without seeing if a treatment helps. Given it's not possible to overdose on b12 im not sure why the doctors are always so reluctant to try a therapeutic trial.

[Gambit62 Administrator in reply to Cathyjw]

main reason is ignorance and poor understanding of how B12 is metabolised.

However, there are also some reasons to be cautious - although B12 isn't toxic raising serum B12 levels can cause problems in some people and lead to a functional B12 deficiency (where B12 can't get from blood to cell). This can be treated by keeping B12 levels really high - ie on going injections - but it seems far from ideal to be creating a dependency if it isn't established that there is an absorption problem.

as fbirder says - GPCA is prone to false positives so no longer recommended as a test by WHO or by UK standards. However IFab is also a problem test - prone to false negatives 40-60% of time depending on the assay method so a negative is a long way from proving that you don't have B12.

what is the dose of the supplements you are using? and do you have any other vitamin and mineral deficiencies.

Other absorption problems that can lead to a B12 deficiency are coeliacs, crohn's, h pyolori infection and a whole raft of drug interactions.

the overlap with thyorid symptoms is also going to be problematic.

Suggest that you try talking to your GP about it - ossible that they may surprise you and be willing to treat but you won't know if you don't sit down and have a proper conversation with them.

List your symptoms

Be clear on the limitations of serum B12 test - will miss 25% of people who aren't B12 deficient (but also picks up 5% who aren't) if used as a single measure. evaluation of symptoms is important and rule of thumb is that symptoms take precedence over results, particularly if you have neurological symptoms.

Be clear that 25% of people who have B12 deficiency don't initially present with macrocytosis (enlarged and rounder red blood cells) - it's a symptom not a defining characteristic.

Source for stats is BCSH guidelines on diagnosis and treatment of cobalamin and folate deficiencies which your GP (assuming UK based) can access through the BNF) but, if you are UK based can also be accessed here

onlinelibrary.wiley.com/doi...