THE VITAMIN B12 AND FOLATE PATHOLOGY INVESTIGATION
THE INVESTIGATION OF ERRORS IN PATHOLOGY TESTS
FOR VITAMIN B12 AND FOLATE DEFICIENCY
BY MEANS OF MEDICAL EXPERIMENTS
B12 AND FOLATE INFORMATION
B12 NOTES
Serum B12
Limitations in Diagnosis
Tests
Treatment
Sources of Information

Serum vitamin B12 is a very poor indicator of vitamin B12 deficiency; it is neither sufficiently sensitive not sufficiently specific. The serum B12 test therefore often gives falsely high results, failing to detect the presence of an actual tissue deficiency.

These are the problems with using serum B12 for diagnosis of vitamin B12 deficiency:

  • There is significant variation in results between labs, and sometimes within a lab - automated immunoassays have significant problems with precision and accuracy
  • Serum B12 only indicates body stores of vitamin B12 if it is in equilibrium with the body stores - it is affected by any recent supplements or injections
  • Body stores do not indicate how much B12 is actually available to the cells - the proportion of B12 on transport proteins, active B12 (holotranscobalamin), falls as deficiency develops
  • The amount of active B12 (holotranscobalamin) does not indicate the ability of the cells to utilize the B12

The serum B12 result therefore says very little about cellular deficiency. For this reason, many experts advocate the use of the two metabolic markers, methylmalonic acid and homocysteine, for diagnosis of vitamin B12 deficiency.

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