Which test was used for the diagnosis: serum B12 (normal/total) or Active B12 (holotranscobalamin)?
However, there is a large “grey” area where a deficiency is possible in spite of a normal B12 serum level.
41.5% of the patients from our survey had a serum B12 level below 100 pmol/L which is an obvious deficiency. Of these patients 23% were not treated immediately, with all the risks that this entails.
What was the level of serum B12?
What was the level of Active B12?
Of the patients who have been tested and knew their results, 20% had an extremely low level of under 10 pmol/L, 26% had a level between 10 and 20 pmol/L and 35% had a level between 20 and 35 pmol/L.
The official reference value for Active B12 in the Netherlands is 21 pmol/L. In the international scientific literature it generally is 35 pmol/L. Levels below 35 pmol/L would very probably mean a deficiency.
Between the 35 and 50 pmol/L is seen as a “grey” area, which requires further testing by means of MMA, at least.