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HelpTest Code ROXUR Oxalate, Random, Urine
Ordering Guidance
A timed 24-hour urine collection is the preferred specimen for measuring and interpreting this urinary analyte. Order OXU / Oxalate, 24 Hour, Urine.
Random collections normalized to urinary creatinine may be of some clinical use in patients who cannot collect a 24-hour specimen, typically small children. Therefore, this random test is offered for children under 16 years old.
Specimen Required
Patient Preparation: Avoid taking large doses (>2 g orally/24 hours) of vitamin C prior to specimen collection.
Supplies: Urine Tubes, 10 mL tube (T068)
Container/Tube: 10-mL plastic tube or a clean, plastic container with no metal cap
Specimen Volume: 7 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative.
3. Specimen pH should be between 4.5 and 8 and will stay in this range if kept refrigerated. Specimens with pH above 8 may indicate bacterial contamination, and testing will be cancelled. Do not attempt to adjust pH as it will adversely affect results.
Useful For
Monitoring therapy for kidney stones using random urine specimens
Identifying increased urinary oxalate as a risk factor for stone formation
Diagnosis of primary or secondary hyperoxaluria
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| OXCO1 | Oxalate, Random, U (mmol/L) | No | Yes |
| OXCO3 | Oxalate, Random, U (mg/L) | No | Yes |
| CRETR | Creatinine, Random, U | No | Yes |
| RAT11 | Oxalate/Creatinine Ratio | No | Yes |
Method Name
OXCO1: Enzymatic Using Oxalate Oxidase
CRETR: Enzymatic Colorimetric Assay
OXCO3, RAT11: Calculation
Reporting Name
Oxalate, Random, USpecimen Type
UrineSpecimen Minimum Volume
6 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Frozen | 14 days | ||
| Ambient | 72 hours |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Oxalate is an end product of glyoxalate and glycerate metabolism. Humans have no 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.
Since increased urinary oxalate excretion promotes calcium oxalate stone formation, various strategies are employed to lower oxalate excretion.
Reference Values
No established reference values
Interpretation
An elevated urine oxalate (>0.46 mmol/day) 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.
The urinary oxalate creatinine ratio varies widely in young children from below 0.35 mmol/mL at birth, to below 0.15 mmol/mL at 1 year of age, to below 0.10 mmol/mL at 10 years of age, and below 0.05 mmol/mL at 20 years of age (see table below).(1)
Table. Oxalate/Creatinine (mg/mg)
|
Age (year) |
95th Percentile |
|
0-0.5 |
<0.175 |
|
0.5-1 |
<0.139 |
|
1-2 |
<0.103 |
|
2-3 |
<0.08 |
|
3-5 |
<0.064 |
|
5-7 |
<0.056 |
|
7-17 |
<0.048 |
Cautions
Ingestion of ascorbic acid (>2 g/day) may falsely elevate the measured urinary oxalate excretion.
Do not collect in metal-capped containers.
Method Description
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)
Day(s) Performed
Monday through Saturday
Report Available
3 to 5 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
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
83945
82570
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| ROXUR | Oxalate, Random, U | 15086-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CRETR | Creatinine, Random, U | 2161-8 |
| OXCO1 | Oxalate, Random, U (mmol/L) | 15086-2 |
| OXCO3 | Oxalate, Random, U (mg/L) | 2700-3 |
| RAT11 | Oxalate/Creatinine Ratio | 13483-3 |
Disease States
- Hyperoxaluria