Diagnostic of of vitamin B12 deficiency
Tests to prove the vitamin B12 deficiency
HOW TO TEST THE DEFICIT OF VITAMIN B12 OR COBALAMINE
How is a vitamin B12 deficiency known?
Deficiency of vitamin B12 (cobalamin) is a serious illness that must always be diagnosed and treated by a doctor. Fortunately, this deficit is easy to prevent by supplementing risk populations that may present a deficit B12:
Risk of vitamin B12 deficiency
The doctor can initially intuit a possible deficit of this vitamin if the person fulfills any of the following characteristics:
- People who follow a vegan diet (without food of animal origin)
- People who follow a vegetarian diet (low consumption of eggs and dairy)
- People following a diet with very few products of animal origin
- Pregnant and lactating women, especially if they are vegetarian
- Vegetarian babies, children and youth, who have high B12 requirements
- Infants, children and young people whose parents follow a vegetarian diet, even if they are not strictly vegetarian
- Elderly, even if they are not vegetarians, because with age decreases absorption capacity
Diagnosis of vitamin B12 deficiency
The doctor is the person in charge of diagnosing a deficiency of vitamin B12. For this, the doctor will perform a physical examination, evaluation of symptoms and blood tests. Urine tests may also be needed.
How is vitamin B12 deficiency or insufficiency determined?
It is recommended that vegetarians perform a specific analysis to determine the levels of this vitamin in the body. Generally the analysis consists of the following parameters:
- Mean corpuscular volume (VCM) of erythrocytes
- Levels of vitamin B12
- Homocysteine levels
- Levels of methylmalonic acid
With these values it is possible to determine the degree of lack of this vitamin that they present, if it is the case.
In severe cases, an encephalogram is performed to see if there are changes in the brain.
VALUES ALTERED IN THE VITAMIN B12 DEFICIT TESTS
Analysis to determine a deficit of B12
There are some values that allow to differentiate the deficit of B12 from the lack of other vitamins or causes that can give the same symptoms. For example, anemia can be due to lack of folic acid (vitamin B9), lack of iron, insufficient diet, digestive diseases or other causes.
It is possible to measure the amount of circulating vitamin B12 in the blood, although the results can be altered if the person consumes algae and foods with vitamin B12 analogues.
All of the following values help diagnose a lack of vitamin B12 or cobalamin:
- Megaloblastic anemia (macrocytic normochromic), low hematocrit
- In severe B12 deficiencies, histological examinations may be altered: Thrombocytopenia, coagulation problems, macrocytosis and neutrophil hypersegmentation
- Neuropathy due to degeneration of the myelin sheath.
Mean corpuscular volume (VCM) of erythrocytes
It tells us the size of erythrocytes or red blood cells. When vitamin B12 is missing, the size of these cells appears slightly increased because they can not be divided.
Although this parameter could be due to the lack or deficit of other vitamins or components, its increase, together with the other values, may indicate a cobalamin deficiency.
High levels of methylmalonic acid
In any vitamin B12 deficiency there is an increase in levels of methylmalonic acid, which is the main characteristic of B12 deficiency, which differentiates it from folic acid deficiency. Vegetarians should analyze what levels of methylmalonic acid present to determine possible subclinical B12 deficits.
The increase in methylmalonic acid is due to the lack of activity of the methylmalonyl-CoA mutase enzyme, which requires cobalamin (vitamin B12) as the coenzyme to produce Succinyl-CoA (which will subsequently be used to form erythrocytes).
Therefore, methylmalonic acid accumulates because Succinyl-CoA can not be formed, because of the decreased activity of the enzyme methylmalonyl-CoA mutase, which uses B12 as cofactor. This leads to decreased synthesis of the heme group (no red blood cells can be formed) and decreased gluconeogenesis.
The explanatory scheme of the reaction is as follows:
High levels of methyl citric acid
Methylcyclic acid levels may also appear high in a B12 deficiency. They are formed from PropionylCoA (precursor methylmalonylCoA), due to the increase of methylmalonylCoA, which increases the production of methyl citric acids. This increase can also be produced by other causes and is not determinant if it is not accompanied by other values.
Increased levels of the amino acid glycine
The decrease in Succinyl-CoA substance causes a decrease in heme synthesis and an increase in glycine. This is because glycine and Succinyl-CoA form ALA (delta-aminolevulinic acid), the structure that will later be transformed into porphyrins (heme group of erythrocytes).
The increase in glycine can also be produced by deficits of other nutrients and other causes, so it is not a determinant of B12 deficiency.
High blood homocysteine levels
Homocysteine is a very harmful amino acid for blood to be removed. This process is responsible for vitamin B12 along with folic acid (vitamin B9).
When there is not enough B12 or folic acid, homocysteine accumulates and increases its elimination by urine due to the alteration of the methionine-homocysteine cycle, affected by the B12 deficit. Vitamin B12 is involved in the methylation and conversion of homocysteine to methionine.
Increased homocysteine may also be produced by deficiency of other nutrients (vitamin B9 or folic acid) and other causes.
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This material is for informational purposes only. In case of doubt, consult the doctor.