Test ID: XAN
Xanthine and Hypoxanthine, Urine
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
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
Diagnosis and confirmation of xanthinuria
Evaluation of low serum or urine uric acids
Evaluation of allopurinol treatment in hyperuricemic disorders (eg, Lesch-Nyhan syndrome)
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Diagnosis and confirmation of xanthinuria and evaluation of allopurinol treatment in hyperuricemic disorders. 24-Hour collection.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
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
Hypoxanthine
MOCOD
Molybdenum cofactor deficiency
Xanthine
Xanthine dehydrogenase deficiency
Xanthine oxidase deficiency
Xanthinuria
XDH deficiency
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: 3 mL
Collection Instructions:
1. Collect urine for 24 hours.
2. No preservative.
Additional Information:
1. 24-Hour volume is required.
2. See Urine Preservatives in Special Instructions for multiple collections.
Forms: New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
Urine Preservative Collection Options
| Ambient | No |
| Refrigerated | Yes |
| Frozen | Preferred |
| 6N HCl | No |
| 50% Acetic Acid | No |
| Na2CO3 | No |
| Toluene | No |
| 6N HNO3 | No |
| Boric Acid | No |
| Thymol | No |
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 (preferred) | 7 days |
| Refrigerated | 7 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Xanthine and hypoxanthine are the precursors of uric acid, the end product of purine metabolism. Two inborn errors of metabolism are characterized by elevated excretion of xanthine and hypoxanthine.
Isolated xanthine dehydrogenase (XDH, xanthine oxidase) deficiency: patients with isolated XDH deficiency may remain asymptomatic, but nephrolithiasis due to the insolubility of xanthine, may occur at any age. Some patients also develop a myopathy with crystalline xanthine deposits in muscle.
Combined deficiency of SDH and the related enzyme sulfite oxidase (SO): combined XDH/SO deficiency is also characterized by nephrolithiasis, but more prominently by the symptoms of SO deficiency (isolated SO deficiency also occurs) which include neonatal seizures, myoclonus, lens dislocation, and severe mental retardation. This form of xanthinuria is caused by molybdenum cofactor deficiency, which is required for the activity of both oxidases.
Elevations of xanthine and hypoxanthine and abnormally low levels of uric acid are found in both disorders, while in patients with XDH/SO deficiency sulfites and sulfur-containing metabolites (S-sulfocysteine, thiosulfate, taurine) also accumulate.
Allopurinol, a xanthine oxidase inhibitor that prevents conversion of xanthine to uric acid, is used to treat hyperuricemia.
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.
HYPOXANTHINE
20-100 mcmol/24 hours
XANTHINE
20-60 mcmol/24 hours
Interpretation Provides information to assist in interpretation of the test results
Abnormal concentrations of xanthine and hypoxanthine will be reported along with an interpretation. The interpretation of an abnormal metabolite pattern will include an overview of the results and of their significance, a correlation to available clinical information, possible differential diagnoses, recommendations for additional biochemical testing and confirmatory studies (enzyme assay, molecular analysis), name and phone number of contacts who may provide these studies at the Mayo Clinic or elsewhere, and a number for one of the laboratory directors if the referring physician has additional questions. Increased urinary xanthine and hypoxanthine with low urinary uric acid are characteristic of xanthine oxidase deficiency.
Increased urinary excretion of xanthine, hypoxanthine, and uric acid are indicative of hyperuricemia disorders treated with allopurinol.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Raivio KO, Saksela M, Lapatto R: Xanthine oxidoreductases-Role in human pathophysiology and in hereditary xanthinuria. In The Metabolic and Molecular Bases of Inherited Disease. 8th edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. New York, McGraw-Hill Book Company, 2001, pp 2639-2652
Method Description Describes how the test is performed and provides a method-specific reference
Diluted, filtered urine is mixed with an internal standard (8-13 C Adenine) and analyzed for xanthine and hypoxanthine by liquid chromatography tandem mass spectrometry (LC-MS/MS). LC-MS/MS is performed using a mobile phase composed of 50 mM ammonium formate, ph=5, and 1:1 mixture of 50 mM ammonium formate, ph=5: methanol and run using a gradient. An Xterra MS C18 column (2.1 x 150 mm) is used to separate xanthine and hypoxanthine from the bulk of the specimen matrix. The MS/MS is operated in the selected reaction monitoring (SRM) scanning mode. The ratios of the extracted peak areas of xanthine and hypoxanthine to an internal standard are used to calculate the concentration of xanthine and hypoxanthine present. (Ito T, van Kuilenburg AP, Bootsma AH, et al: Rapid screening of high-risk patients for disorders of purine and pyrimidine metabolism using HPLC-electrospray tandem mass spectrometry of liquid urine or urine-soaked filter paper strips. Clin Chem 2000;46:445-452)
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.
Varies; Batched 1 time per week; 8 a.m.
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.
83789
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 |
|---|---|---|
| 80313 | Xanthine | 41227-0 |
| 3314 | Hypoxanthine | In Process |
| DUR3 | Urine Duration | 13362-9 |
| VL68 | Urine Volume | 3167-4 |
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