What Is a Methylmalonic Acid Test?
Vitamin B-12 is essential for your health. The vitamin
helps to preserve neurological function, maintain red blood cell production,
and aid in normal DNA synthesis. Deficiencies can arise when you don’t get
enough B-12 from your diet or when your body can’t use it properly.
Typically, vitamin B-12 deficiencies can be detected through the
vitamin B-12 test. In people with normal levels who have clinical symptoms of
vitamin B-12 deficiency, additional testing may be needed. Specifically, the
methylmalonic acid test can be used.
What Is the Purpose of the Test?
acid is a compound that reacts with vitamin B-12 to produce coenzyme A (CoA). Coenzyme A is essential to
normal cellular function. When vitamin B-12 deficiencies occur, methylmalonic acid levels increase. Measurement
of methylmalonic acid through the methylmalonic acid test can provide your
doctor with information about an existing vitamin deficiency, especially if the
B-12 deficiency is mild or just beginning.
The methylmalonic acid test
is more sensitive than the vitamin B-12 test. As a result,
it’s better able to identify vitamin B-12 deficiencies at the
lower end of the normal range. According to the American
Association for Clinical Chemistry,
although the methylmalonic
acid test is a very sensitive test for indicating
B-12 deficiency, there is too much variability for it to provide a
clear diagnosis. That’s why it’s often used along with the vitamin B-12
test, or to clarify ambiguous vitamin B-12 test results. It’s
also often performed along with the homocysteine test. Homocysteine is an
important molecule found in very small amounts in the body. Homocysteine must
be metabolized by vitamin
B-12, so low levels of the vitamin (as well as B-6
and folic acid) lead to elevated levels of homocysteine.
When Is the Test Ordered?
The methylmalonic acid test isn’t typically
ordered as part of a routine physical exam. Your doctor may order the test if
the result of your vitamin B-12 test is abnormal. In addition, the test may be
ordered if you have symptoms of vitamin B-12 deficiency. Symptoms of B-12
abnormalities (abnormal walking, usually measured during a standard
(yellowing of the skin or eyes, often seen in people with liver disease)
neuropathy (nerve damage or malfunctioning nerves)
The methylmalonic acid test may also be
ordered if the results of other blood tests are abnormal. For instance,
abnormal results from a homocysteine test may prompt your doctor to order the methylmalonic acid test. The methylmalonic acid test is also
frequently ordered for infants when the doctor suspects the presence of
methylmalonicacidemia. Methylmalonicacidemia is a rare genetic disorder in
up in the bloodstream.
Preparation for the Test
specific preparation is needed for the methylmalonic acid test.
How Is the Test Administered?
The methylmalonic acid test is performed on
blood taken from a standard blood draw. Typically, a doctor or nurse will take
a blood sample from your arm in a clinical setting. The blood will be collected
in a tube and will be sent to a lab for analysis. Once the lab reports the
results, your doctor will be able to provide you with more information about
the results and what they mean.
What Are the Risks of the Test?
undergoing the methylmalonic
may experience some discomfort when the blood sample is drawn. Needle sticks
may result in pain at the injection site during the test. Following the test, you
may experience pain or throbbing at the injection site. Bruising may also occur
after the test is completed.
risks of the methylmalonic
are minimal and can occur with any blood test. Potential, but rare, risks
obtaining a sample, resulting in multiple needle sticks
bleeding at the needle site
as a result of blood loss
of blood under the skin, known as hematoma
of infection where the skin is broken by the needle
Understanding Your Results
results of the methylmalonic
may vary depending on the laboratory that performs the test. In general, normal
levels of methylmalonic acid are between 0.08 and 0.56 mmol/L (millimoles per
liter). Although higher levels of methylmalonic acid may be an indication of
vitamin B-12 deficiency, elevated levels may not warrant immediate treatment.
Your doctor may want to monitor your methylmalonic acid levels to determine if your vitamin B-12
deficiency is progressing. Your doctor may also order additional tests to
determine the cause of the deficiency. These tests include homocysteine and
levels of methylmalonic
the blood may also be an indication of kidney disease. Kidney disease is often
identified through the use of other blood and diagnostic tests. Damage to the kidneys
can prevent the filtering of methylmalonic acid from the blood. This can result in increased levels of methylmalonic acid in the bloodstream.
Therefore, the presence of high methylmalonic acid levels in patients with kidney disease may
not indicate the presence of a vitamin B-12 deficiency. The results of the test
must be discussed with your doctor and evaluated along with other diagnostic
tests to determine if a vitamin B-12 deficiency is present.