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Interpretive Handbook

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Test 9265 :
Amino Acids, Quantitative, Plasma

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Amino acids are the basic structural units that comprise proteins and are found throughout the body. Many inborn errors of amino acid metabolism, including phenylketonuria and tyrosinemia, have been identified. Amino acid disorders can manifest at any time in a person's life, but most become evident in infancy or early childhood. These disorders result in the accumulation or the deficiency of 1 or more amino acids in biological fluids which leads to the clinical signs and symptoms of the particular amino acid disorder.

 

The clinical presentation is dependent upon the specific amino acid disorder. In general, affected patients may experience failure to thrive, neurologic symptoms, digestive problems, dermatologic findings, and physical and cognitive delays. If not diagnosed and treated promptly, amino acid disorders can result in mental retardation and death. 

 

Treatment for amino acid disorders involves very specific dietary modifications. Nonessential amino acids are synthesized by the body, while essential amino acids are not and must be obtained through an individual's diet. Therapeutic diets are coordinated and closely monitored by a dietician and/or physician. They are structured to provide the necessary balance of amino acids with particular attention to essential amino acids and those which accumulate in a particular disorder. Patients must pay close attention to the protein content in their diet and generally need to supplement with medical formulas and foods. Dietary compliance is monitored by periodic analysis of amino acids.

 

In addition, amino acid analysis may have clinical importance in the evaluation of several acquired conditions including endocrine disorders, liver diseases, muscle diseases, neoplastic diseases, neurological disorders, nutritional disturbances, renal failure, and burns.

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluating patients with possible inborn errors of metabolism

 

May aid in evaluation of endocrine disorders, liver diseases, muscle diseases, neoplastic diseases, neurological disorders, nutritional disturbances, renal failure, and burns

Interpretation Provides information to assist in interpretation of the test results

When abnormal results are detected, a detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, elements of differential diagnosis, recommendations for additional biochemical testing, and in vitro confirmatory studies (enzyme assay, molecular analysis), name and phone number of key contacts who may provide these studies at Mayo Clinic or elsewhere, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Reference values are for fasting patients.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Plasma Amino Acid Reference Values (nmol/mL)

Age Groups

<24 Months (n=191)

2-17 Years (n=441)

> or =18 Years (n=148)

Phosphoserine (PSer)

<109

<95

<18

Phosphoethanolamine (PEtN)

<6

<5

<12

Taurine (Tau)

37-177

38-153

42-156

Asparagine (Asn)

25-91

29-87

37-92

Serine (Ser)

69-271

71-208

63-187

Hydroxyproline (Hyp)

8-61

7-35

4-29

Glycine (Gly)

111-426

149-417

126-490

Glutamine (Gln)

316-1020

329-976

371-957

Aspartic Acid (Asp)

2-20

<11

<7

Ethanolamine (EtN)

<70

<64

<67

Histidine (His)

10-116

12-132

39-123

Threonine (Thr)

47-237

58-195

85-231

Citrulline (Cit)

9-38

11-45

17-46

Sarcosine (Sar)

<5

<5

<5

b-Alanine (bAla)

<28

<27

<29

Alanine (Ala)

139-474

144-557

200-579

Glutamic Acid (Glu)

31-202

22-131

13-113

1-Methylhistidine (1MHis)

<11

<20

<28

3-Methylhistidine (3MHis)

<1

<1

2-9

Argininosuccinic Acid (Asa)

<2

<2

<2

Carnosine (Car)

<13

<1

<1

Anserine (Ans)

<1

<1

<1

Homocitruline (Hcit)

<5

<2

<2

Arginine (Arg)

29-134

31-132

32-120

a-Aminoadipic Acid (Aad)

<4

<3

<3

g-Amino-n-butyric Acid (GABA)

<4

<3

<2

b-Aminoisobutyric Acid (bAib)

<9

<5

<5

a-Amino-n-butyric Acid (Abu)

7-28

7-31

9-37

Hydroxylysine (Hyl)

<4

<3

<2

Proline (Pro)

85-303

80-357

97-368

Ornithine (Orn)

20-130

22-97

38-130

Cystathionine (Cth)

<2

<2

<5

Cystine (Cys)

2-32

2-36

3-95

Lysine (Lys)

49-204

59-240

103-255

Methionine (Met)

11-35

11-37

4-44

Valine (Val)

83-300

106-320

136-309

Tyrosine (Tyr)

26-115

31-106

31-90

Homocystine (Hcy)

NA

NA

<5

Isoleucine (IIe)

31-105

30-111

36-107

Leucine (Leu)

48-175

51-196

68-183

Phenylalanine (Phe)

28-80

30-95

35-80

Tryptophan (Trp)

17-75

23-80

29-77

Alloisoleucine (Allolle)

<2

<3

<5

 

Clinical References Provides recommendations for further in-depth reading of a clinical nature

Amino acids. In The Metabolic and Molecular Bases of Inherited Disease. Eighth edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. New York, McGraw-Hill, Inc. 2001, pp 1667-2105


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