Test Catalog

Test Id : AAUCD

Amino Acids, Urea Cycle Disorders Panel, Plasma

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

Differential diagnosis and follow-up of patients with urea cycle disorders


Urea cycle disorders (UCD) are a group of inherited disorders of nitrogen detoxification that result from defects in any of the enzymes involved in the urea cycle.


Disruption of the urea cycle can result in the accumulation of ammonia which is toxic to the nervous system.


Plasma amino acid analysis can be used to aid in the diagnosis of a UCD as well as for follow-up of a known patient.

Method Name
A short description of the method used to perform the test

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Amino Acid, Urea Cycle Panel, P

Lists additional common names for a test, as an aid in searching

Arginase Deficiency



Argininosuccinic Acid

Argininosuccinic Acid Lyase Deficiency

Argininosuccinic Aciduria

Carbamoyl Phosphate Synthetase (CPS) Deficiency



CPS (Carbamoyl Phosphate Synthetase)


N-acetyl Glutamate Synthase (NAGS) Deficiency

NAGS (N-acetyl Glutamate Synthetase)


Ornithine Transcarbamylase (OTC) Deficiency

OTC (Ornithine Transcarbamylase)

UCD (Urea Cycle Disorder)

Urea Cycle Disorder (UCD)

Argininosuccinic Acid Synthetase Deficiency

Gyrate atrophy

Ornithine Aminotransferase (OAT) Deficiency

Specimen Type
Describes the specimen type validated for testing


Necessary Information

1. Patient's age is required.

2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: Fasting (overnight preferred, 4 hours minimum). Infants should be drawn just before next feeding (2-3 hours without total parenteral nutrition if possible).

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Lavender top (EDTA) or green top (lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Centrifuge within 4 hours if specimen is stored at refrigerated temperature and aliquot plasma.

2. Send plasma frozen.


Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.25 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Plasma Frozen (preferred) 14 days

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

Differential diagnosis and follow-up of patients with urea cycle disorders

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

Urea cycle disorders (UCD) are a group of inherited disorders of nitrogen detoxification that result when any of the enzymes in the urea cycle (carbamoylphosphate synthetase I [CPS I], ornithine transcarbamylase [OTC], argininosuccinic acid synthetase, argininosuccinic acid lyase, arginase, or the cofactor producer, N-acetyl glutamate synthetase [NAGS]), have deficient or reduced activity. The role of the urea cycle is to metabolize and clear waste nitrogen, and defects in any of the steps of the pathway can result in an accumulation of ammonia, which can be toxic to the nervous system. The urea cycle is also responsible for endogenous production of the amino acids citrulline, ornithine, and arginine. Infants with a complete urea cycle enzyme deficiency typically appear normal at birth but present in the neonatal period as ammonia levels rise with lethargy, seizures, hyper- or hypoventilation, and ultimately coma or death. Individuals with partial enzyme deficiency may present later in life, typically following an acute illness or other stressors. Symptoms may be less severe and may present with episodes of psychosis, lethargy, cyclical vomiting, and behavioral abnormalities. Patients with impaired ornithine metabolism due to ornithine aminotransferase deficiency may present with childhood onset myopia progressing to vision loss in the 4th to 6th decades of life. Patients may or may not have accompanying hyperammonemia but display marked elevations in plasma ornithine.


All of the UCD are inherited as autosomal recessive disorders, with the exception of OTC deficiency, which is X-linked. UCD may be suspected with elevated ammonia, normal anion gap, and a normal glucose. Plasma amino acids can be used to aid in the diagnosis of UCD and may aid in monitoring treatment effectiveness. Measurement of urinary orotic acid, enzyme activity (CPS I, OTC, or NAGS), and molecular genetic testing can help to distinguish the conditions and allows for diagnostic confirmation.


Acute treatment for UCD consists of dialysis and administration of nitrogen scavenger drugs to reduce ammonia concentration. Chronic management typically involves restriction of dietary protein with essential amino acid supplementation. More recently, orthotopic liver transplantation has been used with success in treating some 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.


< or =23 months: 316-1020 nmol/mL

2-17 years: 329-976 nmol/mL

> or =18 years: 371-957 nmol/mL



< or =23 months: 20-130 nmol/mL

2-17 years: 22-97 nmol/mL

> or =18 years: 38-130 nmol/mL



< or =23 months: 9-38 nmol/mL

2-17 years: 11-45 nmol/mL

> or =18 years: 17-46 nmol/mL



< or =23 months: 29-134 nmol/mL

2-17 years: 31-132 nmol/mL

> or =18 years: 32-120 nmol/mL



<2 nmol/mL

Reference value applies to all ages.

Provides information to assist in interpretation of the test results

The quantitative results of glutamine, ornithine, citrulline, arginine, and argininosuccinic acid with age-dependent reference values are reported without added interpretation. When applicable, reports of abnormal results may contain an interpretation based on available clinical interpretation.

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.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Brusilow SW, Horwich AL. Urea cycle enzymes. In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA. eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw Hill; 2019. Accessed April 18, 2022. https://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=225084071 2. Haberle J, Burlina A, Chakrapani A, et al: Suggested guidelines for diagnosis and management of urea cycle disorders: First revision. OJ Inherit Metab Dis. 2019 Nov;42(6):1192-1230. doi: 10.1002/jimd.12100

3. Valle D, Simell O. The Hyperornithinemias. In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA. eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw Hill; 2019. Accessed April 18, 2022. https://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=225083672

4. Foshci FG, Morelli MC, Savini S, et al: Urea cycle disorders: A case report of a successful liver transplant and a literature review. World J Gastroenterol. 2015 Apr 7;21(13):4063-4068. doi: 10.3748/wjg.v21.i13.4063

5. Ah Mew N, Simpson KL, Gropman AL, et al: Urea Cycle Disorders Overview. In: Adam MP, Ardinger HH, Pagon RA, et al. GeneReviews[Internet]. University of Washington, Seattle; 2003. Updated June 22, 2017. Accessed May 28, 2019. Available at https://www.ncbi.nlm.nih.gov/books/NBK1217/

Method Description
Describes how the test is performed and provides a method-specific reference

Quantitative analysis of amino acids is performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) by labeling amino acids present in plasma, urine, and spinal fluid with aTRAQ Reagent 121. Samples are dried and reconstituted with aTRAQ Reagent 113-labeled Standard Mix. Amino acids are separated and detected by LC-MS/MS. The concentrations of amino acids are established by comparison of their ion intensity (121-labeled amino acids) to that of their respective internal standards (113-labeled amino acids).(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

3 to 5 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

2 weeks

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
AAUCD Amino Acid, Urea Cycle Panel, P 100368-0
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
32440 Glutamine 20643-3
32441 Citrulline 20640-9
32442 Argininosuccinic Acid 32227-1
32443 Arginine 20637-5
32444 Ornithine 20652-4
32445 Interpretation (AAUCD) 49247-0

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports