Amino Acid Profile, Quantitative, 24-Hour Urine
| Amino Acid Profile, Quantitative, 24-Hour Urine | | | |
| Number | | 095646 |
| CPT | | 82139 |
Related Information | | |
| Synonyms | | Amino Acid Fractionation, 24-Hour Urine; Fractionated Amino Acids, 24-Hour Urine; Quantitative Amino Acids, Urine |
| Test Includes | | Alanine; β-alanine; α-amino-N-butyric acid;
α-aminoadipic acid; γ-aminobutyric acid;
β-aminoisobutyric acid; anserine; arginine;
asparagine;
aspartic acid; carnosine; citrulline; cystathionine;
cystine; glutamic acid; glutamine; glycine; histidine;
homocystine; hydroxyproline; isoleucine; leucine; lysine;
methionine; 1-methyl-histidine; 3-methyl-histidine;
ornithine; phenylanine; phosphoethanolamine; phosphoserine;
proline; sarcosine; serine; taurine; threonine; tyrosine;
tryptophan; valine; and interpretation |
| Special Instructions | | State patient's age, sex, 24-hour urine total volume, and
brief clinical history on the request form. |
| Specimen | | Urine (24-hour), frozen |
| Volume | | 10 mL aliquot |
| Minimum Volume | | 1 mL aliquot |
| Container | | Plastic urine container, no preservative |
| Collection | | Instruct patient to void at 8 AM (or 8 PM) and discard the
specimen. Then collect all the urine including the final
specimen voided at the end of the 24-hour collection period
(ie, 8 AM (or 8 PM) the following day). Specimen must be
kept on ice during collection. Mix well. Transport promptly
to the laboratory. Container must be labeled with patient's
name and date and time collection started and finished. To
avoid delays in turnaround time when requesting multiple
tests on frozen samples, please submit separate frozen
specimens for each test requested. |
| Storage Instructions | | Keep urine on ice during collection. Mix well. Send
frozen aliquot to laboratory. |
| Causes for Rejection | | Contamination of urine with fecal material |
| Reference Interval | | See the Amino Acid Appendix for a listing of individual amino
acid reference intervals. |
| Use | | Certain inborn errors result in the loss of a specific
enzyme or transport activity, which is manifest in the
alteration of the normal metabolism of one or more amino
acids. The quantitation of one or more of these
metabolites in biologic fluids is useful for the diagnosis
of these inborn errors of metabolism. The estimated
incidence of all amino acidopathies is 1:6000. This
estimate does not include other inborn errors of metabolism
(ie, organic acid disorders, some urea cycle
disorders, and congenital lactic acidemias), which may
require amino acid analysis for diagnosis and monitoring
of patient treatment.
Increased amino acid
concentrations in plasma may reflect inherited metabolic
abnormalities, as in the tyrosemias or phenylketonuria.
Plasma is the most informative specimen type for the
diagnosis of most amino acidopathies. Serum is
unacceptable as specimens are left to clot at room
temperature, resulting in a variety of artifacts.
Amino acid quantitations in urine are also used to
evaluate inborn errors of metabolism. In most, but not
all, cases where an amino acid is elevated in blood, it
will also be elevated in urine. Some disorders, primarily
those involving defective renal transport, will only
manifest elevated amino acids in urine; however, in
general, urinary amino acid levels are more variable
than plasma levels. For this reason, screening for amino
acidopathies in urine alone is discouraged, unless a
disorder is suspected that only manifests abnormalities in
urine (eg, cystinuria, renal Fanconi syndrome).
Quantitation of amino acids in cerebrospinal fluid
(CSF) is useful in the diagnosis of several disorders, most
notably nonketotic hyperglycemia. CSF samples are most
informative when a plasma sample is collected at the same
time and the ratios of the amino acid concentrations in CSF
to plasma are calculated.
See the Amino Acid Appendix for interpretation tables. |
| Methodology | | High-pressure liquid chromatography (HPLC) separation with
postcolumn Ninhydrin quantitation |
| References | | Bremer,
HJ. Disturbances of Amino Acid Metabolism: Clinical
Chemistry and Diagnosis. 1981. |
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