At a glance

Also known as

Plasma amino acids; urine amino acids

Why get tested?
Testing is most commonly performed in children suspected of having an inborn error of amino acid metabolism (aminoacidopathy). 
 
When to get tested?
Primary aminoacidopathies are inherited disorders resulting from a deficient enzyme or transport protein. Over 30 aminoacidopathies have been described in the medical literature. Symptoms range from relatively benign to severe. Possible clinical presentations include, intellectual disability, seizures, rapid breathing, poor feeding, failure to thrive and vomiting.
 
Sample required?
For plasma amino acids, a blood sample drawn from a vein in your arm, urine amino acids require a urine specimen.
 
Test preparation needed?
None
 

What is being tested?

Amino acids are the building blocks of proteins and form part of our diet. In order to break down or change (metabolise) the amino acids in our body, special proteins called enzymes are needed. If there is a change or mutation in the gene coding for an enzyme, the normal metabolism gets blocked and the amino acid builds up in the body and may be toxic. Plasma or urine amino acid testing separates and measures all the amino acids we make in our bodies or take in from our diet, to identify any changes which may indicate an inborn error of metabolism.
 
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
 

The Test

How is it used?

Amino acid testing allows us to identify if any particular amino acid concentration is high or low which may indicate a problem in the enzymes used to make or break down the amino acid. Depending on the natural history of the disorder, symptoms may be minimised or prevented by early diagnosis and treatment. Treatment may be based on dietary restrictions and/or supplementation with cofactors (e.g., riboflavin or cobalamin) or other substances such as carnitine or sodium benzoate.

When is it requested?

Testing is most commonly performed in children suspected of having an inborn error of amino acid metabolism (aminoacidopathy). If a patient is found to have an aminoacidopathy and starts dietary treatment, regular testing helps to make sure the levels remain under control and nutrition is adequate for growth and development.

What does the test result mean?

Reference ranges vary with age. Increased or decreased levels of certain amino acids will point to different possible aminoacidopathies.  For example, increased glutamine may point to a defect in the urea cycle. The laboratory issuing the report will comment on any important findings.
Having normal concentrations of amino acids does not rule out other inborn errors of metabolism.

Common Questions

Is amino acid testing covered by Medicare?

Amino acid testing is covered by Medicare when used to diagnose or manage patients with inborn errors of metabolism.  

Last Review Date: March 6, 2017