Test Id : OXU
Effective May 14, 2025: This test is temporarily unavailable due to a nationwide reagent issue. The downtime is expected to be >30 days. An alternative test is not available. See test notification here.
Oxalate, 24 Hour, Urine
Useful For
Suggests clinical disorders or settings where the test may be helpful
Monitoring therapy for kidney stones using 24-hour urine collections
Identifying increased urinary oxalate as a risk factor for stone formation
Diagnosis of primary or secondary hyperoxaluria
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
For information see Hyperoxaluria Diagnostic Algorithm.
Method Name
A short description of the method used to perform the test
Enzymatic
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
Aliases
Lists additional common names for a test, as an aid in searching
Oxalate
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
For information see Hyperoxaluria Diagnostic Algorithm.
Specimen Type
Describes the specimen type validated for testing
Urine
Necessary Information
24-hour volume (in milliliters) is required.
ORDER QUESTIONS AND ANSWERS
| Question ID | Description | Answers |
|---|---|---|
| TM17 | Collection Duration | |
| VL15 | Urine Volume |
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Patient Preparation: For 24 hours before, as well as during the collection process, patient should not take large doses (>2 g orally/24 hours) of vitamin C.
Supplies:
-Diazolidinyl Urea (Germall) 5.0 mL (T822)
-Sarstedt Aliquot Tube, 5mL (T914)
Container/Tube: Plastic tube or a clean, plastic aliquot container with no metal cap or glued insert
Specimen Volume: 4 mL
Collection Instructions:
1. Add 5 mL of diazolidinyl urea (Germall) as a preservative at start of collection or refrigerate specimen during and after collection.
2. Collect urine for 24 hours.
3. Mix container thoroughly and aliquot urine into plastic vial.
4. Specimen pH should be between 4.5 and 8 and will stay in this range if kept refrigerated. Specimens with pH above 8 indicate bacterial contamination, and testing will be canceled. Do not attempt to adjust pH, as it will adversely affect results.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Urine Preservative Collection Options
Note: The addition of preservative must occur at the start of collection or application of temperature controls must occur during and after collection.
| Ambient (No additive) | No |
| Refrigerate (No additive) | OK |
| Frozen (No additive) | No |
| 50% Acetic Acid | No |
| Boric Acid | No |
| Diazolidinyl Urea | Preferred |
| 6M Hydrochloric Acid | No |
| 6M Nitric Acid | No |
| Sodium Carbonate | No |
| Thymol | No |
| Toluene | No |
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
1 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
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 |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Ambient | 72 hours | ||
| Frozen | 14 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Monitoring therapy for kidney stones using 24-hour urine collections
Identifying increased urinary oxalate as a risk factor for stone formation
Diagnosis of primary or secondary hyperoxaluria
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
For information see Hyperoxaluria Diagnostic Algorithm.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Oxalate is an end product of glyoxalate and glycerate metabolism. Humans do not have an enzyme capable of degrading oxalate, therefore it must be eliminated by the kidney.
In tubular fluid, oxalate can combine with calcium to form calcium oxalate stones. In addition, high concentrations of oxalate may be toxic to kidney cells.
Increased urinary oxalate excretion results from inherited enzyme deficiencies (primary hyperoxaluria), gastrointestinal disorders associated with fat malabsorption (secondary hyperoxaluria), or increased oral intake of oxalate-rich foods or vitamin C (ascorbic acid).
Since increased urinary oxalate excretion promotes calcium oxalate stone formation, various strategies are employed to lower oxalate excretion.
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.
0.11-0.46 mmol/24 h
9.7-40.5 mg/24 h
The reference value is for a 24-hour collection. Specimens collected for other than a 24-hour period are reported in unit of mmol/L for which reference values are not established.
Reference values have not been established for patients who are younger than 16 years.
Interpretation
Provides information to assist in interpretation of the test results
An elevated urine oxalate (>0.46 mmol/24 hours) may suggest disease states such as secondary hyperoxaluria (fat malabsorption), primary hyperoxaluria (alanine glyoxalate transferase enzyme deficiency, glyceric dehydrogenase deficiency), idiopathic hyperoxaluria, or excess dietary oxalate or vitamin C intake.
In stone-forming patients, high urinary oxalate values, sometimes even in the upper limit of the normal range, are treated to reduce the risk of stone formation.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Ingestion of ascorbic acid (>2 g/24 hours) may falsely elevate the
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Wilson DM, Liedtke RR. Modified enzyme-based colorimetric assay of urinary and plasma oxalate with improved sensitivity and no ascorbate interference: reference values and sample handling procedures. Clin Chem. 1991;37(7):1229-1235
2. Lieske JC, Wang X. Heritable traits that contribute to nephrolithiasis. Urolithiasis. 2019;47(1):5-10
3. Lieske JC, Turner ST, Edeh SN, Smith JA, Kardia SLR. Heritability of urinary traits that contribute to nephrolithiasis. Clin J Am Soc Nephrol. 2014;9(5):943-950
4. Zhao F, Bergstralh EJ, Mehta, RA, et al. Predictors of incident ESRD among patients with primary hyperoxaluria presenting prior to kidney failure. Clin J Am Soc Nephrol. 2016;11(1):119-126
Method Description
Describes how the test is performed and provides a method-specific reference
The assay utilizes oxalate oxidase, which oxidizes oxalate to carbon dioxide and peroxide. In the presence of peroxidase, the peroxide oxidatively couples 3-methyl-2-benzothiazolinone and 3-dimethylaminobenzoic acid to form indamine dye, which is measured spectrophotometrically at 600 nm.(Kasidas GP, Rose GA. Continuous-flow assay for urinary oxalate using immobilized oxalate oxidase. Ann Clin Biochem. 1985;22:412-419; package insert: Oxalate kit. Trinity Biotech; V 11/2017)
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 Saturday
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.
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
Indicates the location of the laboratory that performs the test
Fees :
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 account representative. 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 has been modified from the manufacturer's instructions. Its performance characteristics were 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.
CPT codes are provided by the performing laboratory.
83945
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 |
|---|---|---|
| OXU | Oxalate, 24 Hr, U | 14862-7 |
| 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.
|
|---|---|---|
| OCATE | Oxalate, 24 Hr, U (mmol/24 hr) | 14862-7 |
| OXU1 | Oxalate, 24 Hr, U (mg/24 hr) | 2701-1 |
| TM17 | Collection Duration | 13362-9 |
| VL15 | Urine Volume | 3167-4 |