Background

Amino acid analysis (AAA) test is used to determine the levels of amino acids in the blood, CSF, urine and tissue samples. It is necessary to know the metabolic disease, monitor the nutritional status and to know the biochemical process.

AAA test is used to diagnose and manage the inborn errors of metabolism (IBM), rare genetic disorders which is caused by enzyme deficiency and any change in the amino acid metabolism. Phenylketonuria (PKU), maple syrup urine disease (MSUD), and homocystinuria (HOM) are the common diseases. These conditions can lead to severe developmental, neurological or systemic complication. Neonatal screening program include AAA to detect these disorders in the first few day of the life.

AAA is used in nutrition and dietetics, neurology and psychology and sports medicine. It assists in the assessment of amino acid deficiencies in malnutrition, malabsorption disorders and individuals following specific diets. It contains information about neurotransmitter synthesis and the relationship to diseases like schizophrenia, depression and epilepsy.

Indications/Applications

AAA test is necessary to detect the genetic diseases which can change the metabolism of amino acids. It is known as aminoacidopathies. These can lead to accumulation of toxic substances or deficiency with severe symptoms. Early detection by AAA test can help in treatment like dietary restrictions and enzyme replacement treatment, to prevent severe complications like organ damage, intellectual disability or death specifically in newborn.

AAA test is important to evaluate the nutritional health, in conditions like protein malnutrition, malabsorption syndromes, peripheral nutrition monitoring. Imablance in amino acids can lead to the neurological and psychiatric disease by affecting the synthesis and function of neurotransmitters. This can lead to conditions like seizure, autism spectrum disorders, anxiety, depression and neurodegenerative disorders.

AAA test helps to identify amino acid patterns linked with the organ dysfunction like renal disease and liver disease. It is also used to diagnose primary aminoacidopathies and to screen the secondary aminoacidopathies.

Primary aminoacidopathies are classified as IEM. They are X-linked or autosomal recessive inherited disease. It is caused by the deficiency of enzyme or transport protein. Symptoms are like development and growth delay, learning or intellectual disability, vomiting, seizures, metabolic alkalosis or acidosis, lethargy, hepatic impairment, changes in the consciousness.

This test is performed if you have symptoms like:

Coma, lethargy, vomiting in the neonate, seizures

Failure to thrive

Hyperammonemia

Imbalance in the electrolyte like respiratory alkalosis

developmental delay

Lactic acidemia

Abnormal newborn screening test results

Specific amino acid disease

Reference Range

The normal range of amino acid in plasma (Age specific in μmol/L)

The normal range of amino acid in urine (Age specific in mmol/mol creatinine)

The normal range of amino acid in CSF (Age specific in μmol/L)

Interpretation

Increased levels of one or more than one amino acids can be diagnose of aminoacidopathy. Increased levels of amino acids are linked with the non-inherited diseases like renal tubular disease like Fanconi syndrome and severe liver diseases. Reduced amino acids levels are linked with inherited metabolic disease, poor protein intake, malnutrition, or GI diseases.

Common aminoacidopathies which can be caused because of the increased levels of specific amino acid:

Collection And Panels

Sample type: Blood sample

Sample collection method: Routine venipuncture

Sample collection tube: Green top tube or heparinized tube

Sample volume: 2 mL

Minimum sample volume: 0.25 mL

Unacceptable samples: Grossly hemolyzed samples are not acceptable.

Sample storage: Store the sample in freezing condition at below -20° C.

Instructions: Patient must fast overnight or at least 4 hours before the test. It is necessary to know the age of patient to get the correct range.

Sample type: Urine

Sample collection method: Collect 24 hours of urine samples

Sample collection container: Plastic sterile container

Sample volume: 2 mL

Minimum sample volume: 0.5 mL

Sample type: Cerebrospinal fluid (CSF)

Sample collection method: Lumber puncture

Sample collection tube: Sterile plastic vials

Sample volume: 1 to 2 mL

Modifying factors:

Amino acid levels can be affected by many factors like recent protein-rich meals, medications like corticosteroids or valproic acid, age and development, and underlying conditions like liver disease, kidney dysfunction, and GI disorder.

References

https://pubmed.ncbi.nlm.nih.gov/19937719/

https://pubmed.ncbi.nlm.nih.gov/30459394/