Oxalate:Creatinine Ratio, Random Urine
Use
The Oxalate:Creatinine Ratio in random urine is used to evaluate the risk of kidney stones in patients. It quantifies oxalate levels in relation to creatinine to help assess potential hyperoxaluria and its contribution to stone formation. Hyperoxaluria can be primary or secondary to dietary factors, gastrointestinal absorption, or metabolic disorders, impacting kidney stone risk.
Special Instructions
State patient's age and sex on the test request form and the specimen container. Specimens submitted without preservative should be acidified after receipt to pH ≤3 with 6N HCl prior to aliquoting.
Limitations
Urine samples not maintained at a pH ≤3 may have oxalate levels altered due to spontaneous crystallization or conversion of ascorbate to oxalate. The test results can be influenced by vitamin C intake; patients should avoid vitamin C supplements and rich foods 48 hours prior to sample collection.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 13483-3
- 2700-3
- 2161-8
- 13483-3
Result Turnaround Time
4-7 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
10 mL
Minimum Volume
2.5 mL
Container
Random urine transport tube or urine Monovette® with pH stabilizer (Labcorp No. 56015)
Collection Instructions
Collect urine and transfer to a random urine transport tube or urine Monovette® with pH stabilizer (Labcorp No. 56015).
Patient Preparation
Avoid vitamin C supplements and vitamin C-rich foods (e.g., citrus fruits like oranges, orange juice; vegetables like broccoli, tomatoes, peppers, potatoes) for 48 hours prior to collection.
Storage Instructions
Maintain acidified urine at room temperature. Acid prevents crystallization and conversion of ascorbate to oxalate.
Causes for Rejection
Urine sample received with a pH not ≤3 from a patient on high doses of vitamin C
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 7 days |
| Frozen | 8 weeks |