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Interpretive Handbook

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Test 81934:
Amino Acids, Quantitative, Spinal Fluid

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

Many genetic errors affecting amino acid metabolism have been identified. Defects of either transport or catalytic activity of enzymes involved in this pathway result in accumulation or excessive loss of 1 or more amino acids in biological fluids. Inborn errors of amino acid metabolism can manifest themselves at anytime in a person’s life, but most become evident in infancy and early childhood. Affected patients may have failure to thrive, neurological symptoms, digestive problems, locomotor retardation, and a wide spectrum of laboratory findings. If not diagnosed promptly and treated properly, these disorders can result in poor growth, mental retardation, and death.

 

Cerebrospinal fluid (CSF) specimens are highly informative for a subset of these conditions, such as nonketotic hyperglycinemia and serine biosynthesis defects. CSF specimens are most informative when a plasma specimen is drawn at the same time and the ratio of the amino acid concentrations in CSF to plasma is calculated.

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

Evaluating patients with possible inborn errors of amino acid metabolism, in particular nonketotic hyperglycemia and serine biosynthesis defects, especially when used in conjunction with concomitantly drawn plasma specimens

Interpretation Provides information to assist in interpretation of the test results

When no significant abnormalities are detected, a simple descriptive interpretation is provided. When abnormal results are detected, a detailed interpretation is given. This interpretation includes an overview of the results and their significance, a correlation to available clinical information, elements of differential diagnosis, and 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 the telephone 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

Proper specimen collection and handling are crucial to achieve reliable results. Blood contamination can interfere with test results.

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.

CSF Amino Acid Reference Values (nmol/mL)

Age Groups

< or =31 Days
(n=73)

32 Days-23 Months
(n=88)

2-18 Years
(n=189)

> or =19 Years
(n=32)

Phosphoserine (PSer)

<1

<1

<1

<1

Phosphoethanolamine (PEtN)

<15

<10

<8

<7

Taurine (Tau)

8-48

<28

<13

<20

Asparagine (Asn)

8-34

5-16

<10

5-20

Serine (Ser)

44-136

26-71

21-51

19-40

Hydroxyproline (Hyp)

<7

<3

<1

<2

Glycine (Gly)

5-115

<33

<11

<35

Glutamine (Gln)

467-1832

301-1128

326-1092

380-1348

Aspartic Acid (Asp)

<1

<1

<1

<2

Ethanolamine (EtN)

11-193

7-155

7-153

7-153

Histidine (His)

11-70

9-28

9-21

9-28

Threonine (Thr)

32-143

11-77

14-38

23-57

Citrulline (Cit)

<11

<6

<3

<9

Sarcosine (Sar)

<1

<1

<1

<1

Beta-alanine (bAla)

<26

<25

<25

<25

Alanine (Ala)

24-124

16-53

12-34

19-60

Glutamic Acid (Glu)

<12

<3

<1

<4

1-Methylhistidine (1MHis)

<3

<1

<2

<3

3-Methylhistidine (3MHis)

<4

<1

<1

<2

Argininosuccinic Acid (Asa)

<1

<2

<1

<1

Carnosine (Car)

<1

<1

<1

<1

Anserine (Ans)

<9

<9

<7

<3

Homocitrulline (Hcit)

<3

<1

<1

<1

Arginine (Arg)

5-39

11-35

11-27

11-32

Alpha-aminoadipic Acid (Aad)

<1

<1

<1

<1

Gamma-amino-n-butyric Acid (GABA)

<1

<1

<1

<1

Beta-aminoisobutyric Acid (bAib)

<1

<1

<1

<1

Alpha-amino-n-butyric Acid (Abu)

<15

<6

<5

<14

Hydroxylysine (Hyl)

<1

<1

<1

<1

Proline (Pro)

<17

<6

<2

<6

Ornithine (Orn)

<24

<12

<6

<11

Cystathionine (Cth)

<1

<2

<1

<1

Cystine (Cys)

<2

<2

<1

<1

Lysine (Lys)

11-63

9-33

10-25

13-42

Methionine (Met)

<43

<9

<6

<10

Valine (Val)

14-61

9-28

8-20

11-40

Tyrosine (Tyr)

8-83

5-24

<17

5-17

Homocystine (Hcy)

<1

<1

<1

<1

Isoleucine (Ile)

<27

<13

<8

<17

Leucine (Leu)

12-41

6-21

7-16

7-29

Phenylalanine (Phe)

7-40

5-18

<12

7-21

Tryptophan (Trp)

<12

<6

<4

<4

Allo-isoleucine (AlloIle)

<3

<2

<2

<2

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

Rinaldo P, Hahn S, Matern D: Inborn errors of amino acid, organic acid, and fatty acid metabolism. In Tietz Textbook of Clinical Chemistry and Molecular Diagnosis. Fourth edition. Edited by CA Burtis, ER Ashwood, DE Bruns. St. Louis, WB Saunders Company, 2005, pp 2207-2247