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
Tests
Summary and Explanation
Treatment
Sources of Information

Index

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Summary of Tests

Most of the tests that I suggest come from the articles, Vitamin B12 Deficiency and Laboratory Diagnosis of Vitamin B12 and Folate Deficiency; they are references DA01and DA02 on my References page. The test for Active B12 is explained in Active-B12 (holotranscobalamin), my reference EB03.

These are the tests:

  • Total serum B12
  • Active B12 (holotranscobalamin, HoloTC)
  • Serum Methylmalonic Acid (MMA)
  • Total Homocysteine (tHcy)
  • Intrinsic Factor Antibodies
  • Parietal Cell Antibodies

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Explanation of Tests

Total serum B12

Total serum B12 is not sufficiently sensitive or specific to be a reliable indicator of vitamin B12 deficiency. This means that the serum B12 level can be high although there is an actual deficiency of B12 available to the cells that need it.

Total serum B12 is considered to be an indicator of total body stores of vitamin B12. It is therefore useful to measure the total B12 before and after commencement of treatment.

Active B12 (holotranscobalamin, HoloTC)

Active B12 is a new test that measures only the part of the serum B12 that is available for transport to the cells. Because this part is only typically 10% to 30% of the total, it should be a more sensitive indicator of actual vitamin B12 deficiency. This test is explained in detail in reference EB03 on the References page, Active-B12 (holotranscobalamin), Axis Shield.

I have investigated the actual performance of the active B12 (holotranscobalamin) test, compared to total B12, MMA and tHcy, and have reported the results in THE HOLOTRANSCOBALAMIN INVESTIGATION.

Serum Methylmalonic Acid (MMA)

Methylmalonic Acid is used as a metabolic marker for vitamin B12 deficiency. MMA is increased in the blood when a cellular deficiency of vitamin B12 reduces the rate of reaction. This has the double effect of decreasing the production of essential chemicals and increasing the amount of toxic MMA.

MMA has the advantage of not being affected by folate deficiency, unlike the other metabolite, homocysteine. It has the disadvantages of high cost and being available in fewer laboratories; only five labs in Australia perform MMA analyses.

Total Homocysteine (tHcy)

Homocysteine is another metabolic marker for vitamin B12 deficiency. The level of homocysteine is increased in the blood when a cellular deficiency of vitamin B12 reduces the rate of reaction. As for MMA, this has the double effect of decreasing the production of essential chemicals and increasing the amount of toxic homocysteine.

Homocysteine is also affected by folate deficiency, so cannot be used alone to diagnose vitamin B12 deficiency. The advantage of using homocysteine is that the test is low in cost and commonly available.

Intrinsic Factor Antibodies and Parietal Cell Antibodies

These tests for antibodies are used to assist in the diagnosis of Pernicious Anaemia (PA), a significant cause of vitamin B12 deficiency. A positive result for both tests is generally considered to be diagnostic of PA; a negative result does not rule it out.

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Diagnostic Flowchart

This is the diagnostic flowchart from reference DA01:

Oh and Brown, reference DA01

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