Amino Acid Analysis

Amino Acid Analysis

This test summary provides information on the use of amino acid analysis to screen for or diagnose inherited metabolic disorders.

See also 5 related tests 0 related guides Test Guide List

Amino Acid Analysis

Test Summary

 

Amino Acid Analysis

Test codes: 767 [plasma], 36183 [urine], 29881 [CSF], 1776 [limited, plasma], 19779 [MSUD, plasma]

 

Clinical use

  • Screen for and diagnose disorders of amino acid metabolism
  • Monitor therapeutic response
  • Assess nutritional status

Clinical background

Disorders of amino acid metabolism form a large category within a wider group of inherited metabolic disorders.1 They are typically autosomal recessive or X-linked inherited disorders resulting from a deficient enzyme or transport protein.2,3 

Symptoms range from relatively benign to severe and may include, but are not limited to, growth and developmental delay, intellectual disability, learning disabilities, seizures, vomiting, metabolic acidosis or alkalosis, hepatic impairment, lethargy, and alteration of consciousness.2,3 Depending on the natural history of the disorder, symptoms may be minimized or prevented by early diagnosis.

In several disorders of amino acid metabolism, treatment during the presymptomatic and early symptomatic stages can prevent irreversible organ damage and improve outcomes.4 Treatment may include dietary restrictions and/or supplementation with cofactors (eg, riboflavin or cobalamin) or amino acids (eg, citrulline, arginine), enzyme substitution therapy, or conjugating agents (eg, ammonia scavengers).

Quest Diagnostics offers amino acid analysis panels (Table 1),2,3,5 which range from small panels to diagnose specific disorders of amino acid metabolism (eg, maple syrup urine disease [MSUD]) to broad panels, to screen for or diagnose inherited metabolic disorders of unclear etiology. Panels can also be used to simultaneously monitor multiple amino acids in response to therapy. Choice of specimen type (plasma, cerebrospinal fluid [CSF], urine) depends on the disorder. Plasma is the preferred specimen type for diagnosing most disorders of amino acid metabolism, whereas urine and CSF specimens are useful for diagnosing certain disorders (Table 1).2,3,5

Table 1. Amino Acid Analysis Panelsa

Test code

Test name

Component tests

Clinical use2,3,5 

Plasma

19779

Amino Acid Analysis for MSUD, Plasmab

Alloisoleucine, isoleucine, leucine, valine
  • Diagnose MSUD
  • Monitor therapeutic response

1776

Amino Acid Analysis, Limited, Plasma

Isoleucine, leucine, phenylalanine, tyrosine, tryptophan, valine
  • Monitor patients with phenylalanine hydroxylase deficiency

767

Amino Acid Analysis, Plasma

Alanine, β-alanine, α-aminoadipic acid, α-aminobutyric acid, γ-aminobutyric acid, β-aminoisobutyric acid, arginine, asparagine, aspartic acid, citrulline, cystathionine, ethanolamine, glutamic acid, glutamine, glycine, histidine, homocystine, hydroxyproline, isoleucine, leucine, lysine, methionine, 1-methylhistidine, 3-methylhistidine, ornithine, phenylalanine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine, valine
  • Diagnose disorders of amino acid metabolism (preferred specimen)
  • Monitor therapeutic response
  • Assess nutritional status in patients with nonmetabolic conditions such as short-bowel syndrome

Urine

36183

Amino Acid Analysis, LC/MS, Urineb

Alanine, β-alanine, α-aminoadipic acid, α-aminobutyric acid, γ-aminobutyric acid, arginine, β-aminoisobutyric acid, asparagine, aspartic acid, citrulline, creatinine, cystathionine, cystine, ethanolamine, glutamic acid, glutamine, glycine, histidine, homocystine, hydroxylysine, hydroxyproline, isoleucine, leucine, lysine, methionine, 1-methylhistidine, 3-methylhistidine, ornithine, phenylalanine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine, valine
  • Diagnose disorders of renal amino acid transport

CSF

29881

Amino Acid Analysis, LC/MS, CSFb

Alanine, β-alanine, α-aminoadipic acid, α-aminobutyric acid, γ-aminobutyric acid, β-aminoisobutyric acid, arginine, asparagine, aspartic acid, citrulline, glutamic acid, glutamine, glycine, histidine, homocystine, hydroxyproline, isoleucine, leucine, lysine, methionine, ornithine, phenylalanine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine, valine

  • Diagnose
  • Glycine encephalopathy (nonketotic hyperglycinemia)
  • Serine deficiency
  • Asparagine and glutamine synthetase deficiencies
CSF, cerebrospinal fluid; LC/MS, liquid chromatography/mass spectrometry; MSUD, maple syrup urine disease.
a This test listing is not intended to be comprehensive. For additional testing options, consult TestDirectory.QuestDiagnostics.com.
b This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

 

Additional assistance in test selection is available from Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463).

Individuals suitable for testing

  • Neonates/infants, children, and adults who
  • Exhibit signs and symptoms of an inherited metabolic disorder
  • Exhibit signs and symptoms of nutritional deficiency
  • Are monitored for an established diagnosis of an inherited metabolic disorder
  • Neonates/infants with an abnormal newborn screen being evaluated for a possible inherited metabolic disorder

Method

  • Liquid chromatography, mass spectrometry (LC/MS)
  • Analytical sensitivity: limit of quantitation (LOQ) 1-6 mmol/L, depending on the analyte
  • Analytical specificity: no known cross-reaction with other substances
  • Reportable range: from LOQ to 2,500-25,000 mmol/L, depending on the analyte (urine values reported as mmol/mol creatinine)

Interpretive information

Amino acid levels are compared with age-specific reference ranges (Tables 2-4). Interpretation of the results is based on patterns of relatively high or low levels of specific amino acids.2 Additional laboratory testing may be needed to diagnose disorders of amino acid metabolism or other inherited metabolic disorders.2,5 Results should be considered together with clinical findings, patient history, and other laboratory data. Additional assistance in interpretation of results is available from Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463).

Table 2. Plasma Amino Acid Age-Specific Reference Ranges (μmol/L)
Table 3. Urine Amino Acid Age-Specific Reference Ranges (mmol/mol creatinine)
Table 4. CSF Amino Acid Age-Specific Reference Ranges (μmol/L)

Infant formulas that are supplemented with amino acids (particularly methionine and homocitrulline) and parenteral nutrition may affect the clinical accuracy of this test. Bacterial contamination of specimens and certain medications, such as valproic acid, can also affect the levels of specific amino acids. In addition, the absence of a protein-containing diet in newborns may preclude detection of selected disorders of amino acid metabolism.

References

  1. Ferreira CR, Rahman S, Keller M, et al. An international classification of inherited metabolic disorders (ICIMD). J Inherit Metab Dis. 2021;44(1):164-177. doi:10.1002/jimd.12348
  2. Sharer JD, Biase ID, Matern D, et al. Laboratory analysis of amino acids, 2018 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG). Genet Med. 2018;20(12):1499-1507. doi:10.1038/s41436-018-0328-6
  3. Pasquali M, Longo N. Newborn screening and inborn errors of metabolism. In: Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier Inc; 2022.
  4. Yudkoff M. Disorders of amino acid metabolism. In: Brady S, ed. Basic Neurochemistry. 8th ed. Academic Press; 2012:737-754. doi:10.1016/b978-0-12-374947-5.00042-0
  5. Prinsen HCMT, Huigen MCDG. Amino acids. In: Laboratory Guide to the Methods in Biochemical Genetics. 2nd ed. Springer; 2024:43-64.
     

Content reviewed 1/2026

top of page

This test summary provides information on the use of amino acid analysis to screen for or diagnose inherited metabolic disorders.

Test Guide List

Amino Acid Analysis

Test Summary

 

Amino Acid Analysis

Test codes: 767 [plasma], 36183 [urine], 29881 [CSF], 1776 [limited, plasma], 19779 [MSUD, plasma]

 

Clinical use

  • Screen for and diagnose disorders of amino acid metabolism
  • Monitor therapeutic response
  • Assess nutritional status

Clinical background

Disorders of amino acid metabolism form a large category within a wider group of inherited metabolic disorders.1 They are typically autosomal recessive or X-linked inherited disorders resulting from a deficient enzyme or transport protein.2,3 

Symptoms range from relatively benign to severe and may include, but are not limited to, growth and developmental delay, intellectual disability, learning disabilities, seizures, vomiting, metabolic acidosis or alkalosis, hepatic impairment, lethargy, and alteration of consciousness.2,3 Depending on the natural history of the disorder, symptoms may be minimized or prevented by early diagnosis.

In several disorders of amino acid metabolism, treatment during the presymptomatic and early symptomatic stages can prevent irreversible organ damage and improve outcomes.4 Treatment may include dietary restrictions and/or supplementation with cofactors (eg, riboflavin or cobalamin) or amino acids (eg, citrulline, arginine), enzyme substitution therapy, or conjugating agents (eg, ammonia scavengers).

Quest Diagnostics offers amino acid analysis panels (Table 1),2,3,5 which range from small panels to diagnose specific disorders of amino acid metabolism (eg, maple syrup urine disease [MSUD]) to broad panels, to screen for or diagnose inherited metabolic disorders of unclear etiology. Panels can also be used to simultaneously monitor multiple amino acids in response to therapy. Choice of specimen type (plasma, cerebrospinal fluid [CSF], urine) depends on the disorder. Plasma is the preferred specimen type for diagnosing most disorders of amino acid metabolism, whereas urine and CSF specimens are useful for diagnosing certain disorders (Table 1).2,3,5

Table 1. Amino Acid Analysis Panelsa

Test code

Test name

Component tests

Clinical use2,3,5 

Plasma

19779

Amino Acid Analysis for MSUD, Plasmab

Alloisoleucine, isoleucine, leucine, valine
  • Diagnose MSUD
  • Monitor therapeutic response

1776

Amino Acid Analysis, Limited, Plasma

Isoleucine, leucine, phenylalanine, tyrosine, tryptophan, valine
  • Monitor patients with phenylalanine hydroxylase deficiency

767

Amino Acid Analysis, Plasma

Alanine, β-alanine, α-aminoadipic acid, α-aminobutyric acid, γ-aminobutyric acid, β-aminoisobutyric acid, arginine, asparagine, aspartic acid, citrulline, cystathionine, ethanolamine, glutamic acid, glutamine, glycine, histidine, homocystine, hydroxyproline, isoleucine, leucine, lysine, methionine, 1-methylhistidine, 3-methylhistidine, ornithine, phenylalanine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine, valine
  • Diagnose disorders of amino acid metabolism (preferred specimen)
  • Monitor therapeutic response
  • Assess nutritional status in patients with nonmetabolic conditions such as short-bowel syndrome

Urine

36183

Amino Acid Analysis, LC/MS, Urineb

Alanine, β-alanine, α-aminoadipic acid, α-aminobutyric acid, γ-aminobutyric acid, arginine, β-aminoisobutyric acid, asparagine, aspartic acid, citrulline, creatinine, cystathionine, cystine, ethanolamine, glutamic acid, glutamine, glycine, histidine, homocystine, hydroxylysine, hydroxyproline, isoleucine, leucine, lysine, methionine, 1-methylhistidine, 3-methylhistidine, ornithine, phenylalanine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine, valine
  • Diagnose disorders of renal amino acid transport

CSF

29881

Amino Acid Analysis, LC/MS, CSFb

Alanine, β-alanine, α-aminoadipic acid, α-aminobutyric acid, γ-aminobutyric acid, β-aminoisobutyric acid, arginine, asparagine, aspartic acid, citrulline, glutamic acid, glutamine, glycine, histidine, homocystine, hydroxyproline, isoleucine, leucine, lysine, methionine, ornithine, phenylalanine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine, valine

  • Diagnose
  • Glycine encephalopathy (nonketotic hyperglycinemia)
  • Serine deficiency
  • Asparagine and glutamine synthetase deficiencies
CSF, cerebrospinal fluid; LC/MS, liquid chromatography/mass spectrometry; MSUD, maple syrup urine disease.
a This test listing is not intended to be comprehensive. For additional testing options, consult TestDirectory.QuestDiagnostics.com.
b This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

 

Additional assistance in test selection is available from Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463).

Individuals suitable for testing

  • Neonates/infants, children, and adults who
  • Exhibit signs and symptoms of an inherited metabolic disorder
  • Exhibit signs and symptoms of nutritional deficiency
  • Are monitored for an established diagnosis of an inherited metabolic disorder
  • Neonates/infants with an abnormal newborn screen being evaluated for a possible inherited metabolic disorder

Method

  • Liquid chromatography, mass spectrometry (LC/MS)
  • Analytical sensitivity: limit of quantitation (LOQ) 1-6 mmol/L, depending on the analyte
  • Analytical specificity: no known cross-reaction with other substances
  • Reportable range: from LOQ to 2,500-25,000 mmol/L, depending on the analyte (urine values reported as mmol/mol creatinine)

Interpretive information

Amino acid levels are compared with age-specific reference ranges (Tables 2-4). Interpretation of the results is based on patterns of relatively high or low levels of specific amino acids.2 Additional laboratory testing may be needed to diagnose disorders of amino acid metabolism or other inherited metabolic disorders.2,5 Results should be considered together with clinical findings, patient history, and other laboratory data. Additional assistance in interpretation of results is available from Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463).

Table 2. Plasma Amino Acid Age-Specific Reference Ranges (μmol/L)
Table 3. Urine Amino Acid Age-Specific Reference Ranges (mmol/mol creatinine)
Table 4. CSF Amino Acid Age-Specific Reference Ranges (μmol/L)

Infant formulas that are supplemented with amino acids (particularly methionine and homocitrulline) and parenteral nutrition may affect the clinical accuracy of this test. Bacterial contamination of specimens and certain medications, such as valproic acid, can also affect the levels of specific amino acids. In addition, the absence of a protein-containing diet in newborns may preclude detection of selected disorders of amino acid metabolism.

References

  1. Ferreira CR, Rahman S, Keller M, et al. An international classification of inherited metabolic disorders (ICIMD). J Inherit Metab Dis. 2021;44(1):164-177. doi:10.1002/jimd.12348
  2. Sharer JD, Biase ID, Matern D, et al. Laboratory analysis of amino acids, 2018 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG). Genet Med. 2018;20(12):1499-1507. doi:10.1038/s41436-018-0328-6
  3. Pasquali M, Longo N. Newborn screening and inborn errors of metabolism. In: Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier Inc; 2022.
  4. Yudkoff M. Disorders of amino acid metabolism. In: Brady S, ed. Basic Neurochemistry. 8th ed. Academic Press; 2012:737-754. doi:10.1016/b978-0-12-374947-5.00042-0
  5. Prinsen HCMT, Huigen MCDG. Amino acids. In: Laboratory Guide to the Methods in Biochemical Genetics. 2nd ed. Springer; 2024:43-64.
     

Content reviewed 1/2026

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Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.

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