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Blood test
Blood test

Methylmalonic acid
Definition:
A test that measures the amount of methylmalonic acid in serum.

How the test is performed:

Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The blood is then sent to the laboratory for analysis
How to prepare for the test:
Adult:
No special preparation is necessary.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed:
This test is used to look for methylmalonic acid in the blood. Elevated levels of this chemical occurs in certain genetic disorders and Vitamin B12 deficiency.
Normal Values:
Normal serum methylmalonic acid levels are 0.08 to 0.56 micromoles/L. Values greater than this normal range supports Vitamin B12 deficiency or a genetic disease resulting high levels of methylmalonic acid (methylmalonic aciduria).
What abnormal results mean:
What the risks are:
  • excessive bleeding
  • fainting or feeling light-headed
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins
Special considerations:
Two enzymes are involved in the conversion of propionyl CoA (formed from amino acid metabolism) to methylmalonyl CoA. In addition, biotin and (Vitamin B12) cobalamin are needed as cofactors. Inherited deficiencies of these necessary enzymes cause severe metabolic abnormalities (ketoacidosis).

Normally methylmalonic acid and its precursor (propionic acid) are found in very small amounts in body fluids because methylmalonyl CoA is converted to succinyl CoA, which is further metabolized to produce energy or is involved in the synthesis of porphyrins. When methylmalonyl CoA builds up to an abnormal level, an enzyme that converts it to methylmalonic acid becomes active.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Review Date: 2/17/2002
Reviewed By: Michael C. Milone, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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