Test ID: OROT
Orotic Acid, Urine
NY State Approved 
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluation of the differential diagnosis of hyperammonemia and hereditary orotic aciduria
When orotic acid is measured after a protein load or administration of allopurinol, excretion of orotic acid is a very sensitive indicator of ornithine transcarbamylase (OTC) activity. An allopurinol challenge may be helpful in determining whether a female patient may be a carrier of an OTC mutation if molecular genetic testing was not informative.
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Evaluation of the differential diagnosis of hyperammonemia and hereditary orotic aciduria.
Method Name A short description of the method used to perform the test
Colorimetric
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Cit I
Citrullinemia I
Hereditary orotic aciduria
HHH
Hyperornithinemia, hyperammonemia, homocitrullinuria syndrome
LPI
Lysinuric protein intolerance
Ornithine transcarbamylase deficiency
UMPS
Uridine monophosphate synthase deficiency
Urea Cycle Disorder (UCD)
OTC (Ornithine Transcarbamylase)
ASA (Aspirin)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Plastic, 10-mL urine tube (Supply T068)
Specimen Volume: 10 mL
Collection Instructions:
1. Collect a random or timed urine specimen.
2. No preservative.
Additional Information: Patient's age is required.
Forms: If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Urine | Frozen | 30 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The urinary excretion of orotic acid, an intermediate in pyrimidine biosynthesis, is increased in many urea cycle disorders and in a number of other disorders involving the metabolism of arginine. The determination of orotic acid can be useful to distinguish between various causes of elevated ammonia (hyperammonemia). Hyperammonemia is characteristic of all urea cycle disorders, but orotic acid is elevated in only some. Orotic acid is also elevated in the transport defects of dibasic amino acids (lysinuric protein intolerance, and hyperornithinemia, hyperammonemia, homocitrullinuria [HHH] syndrome), and greatly elevated in patients with hereditary orotic aciduria (uridine monophosphate synthase [UMPS] deficiency).
Ornithine transcarbamylase (OTC) deficiency is an X-linked urea cycle disorder that affects both males and females due to random X-inactivation. In OTC deficiency, carbamoyl phosphate accumulates and is alternatively metabolized to orotic acid. Allopurinol inhibits orotidine monophosphate decarboxylase and, when given to OTC carriers (who may have normal orotic acid excretion), can cause increased excretion of orotic acid. A carefully-monitored allopurinol challenge followed by several determinations of a patient's orotic acid excretion can be useful to identify OTC carriers, as approximately 20% of OTC mutations are not detectable by current molecular genetic testing methods.
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.
<2 weeks: 1.4-5.3 mmol/mol creatinine
2 weeks-1 year: 1.0-3.2 mmol/mol creatinine
2-10 years: 0.5-3.3 mmol/mol creatinine
> or =11 years: 0.4-1.2 mmol/mol creatinine
Interpretation Provides information to assist in interpretation of the test results
The value for the orotic acid concentration is reported. The interpretation of the result must be correlated with clinical and other laboratory findings.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Pregnant women will normally excrete up to twice the upper limit of the adult reference range.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Singh RH, Rhead WJ, Smith W, et al: Nutritional management of urea cycle disorders. Crit Care Clin 2005 Oct;21(4 Suppl):S27-35
2. Lee B, Singh RH, Rhead WJ, et al: Considerations in the difficult-to-manage urea cycle disorder patient. Crit Care Clin 2005 Oct;21(4 Suppl):S19-25 Review
3. Brusilow SW, Horwich AL: Urea cycle enzymes. In The Metabolic and Molecular Bases of Inherited Disease. Eighth edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. McGraw-Hill Book Company, 2001, pp 1909-1964
4. Webster DR, Becroft DMO, van Gennip AH, van Kuilenberg ABP: Hereditary orotic aciduria and other disorders of pyrimidine metabolism. In The Metabolic and Molecular Bases of Inherited Disease. Eighth edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. McGraw-Hill Book Company, 2001, pp 2663-2702
5. Harris ML, Oberholzer VG: Conditions affecting the colorimetry of orotic acid and orotidine in urine. Clin Chem 1980;26(3):473-479
Method Description Describes how the test is performed and provides a method-specific reference
Interfering substances such as amino acids, urea, pigments, and creatinine are removed from the urine by passing it through a cation-exchange resin. The orotic acid is then brominated to form dibromobarbituric acid, reduced to barbituric acid with ascorbic acid, and finally condensed with dimethylaminobenzaldehyde to form 5(p-dimethylaminobenzaldehyde)-barbituric acid. The absorbance of the final product is measured at 480 nm using a control reaction as reference.(Harris ML, Oberholzer VG: Conditions affecting the colorimetry of orotic acid and orotidine in urine. Clin Chem 1980;26[3]:473-479)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Tuesday, Thursday; 8am
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
83921
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 8905 | Orotic Acid, U | 30480-8 |
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