Oxalate, Urine 24 Hour
Oxalate, 24-hr urine
Antrim #13190, EPIC: LAB5872, SOFT: OXA24
- Excessive amounts of oxalate rich foods or Vitamin C can interfere with the assay and should be avoided 48 hours prior to urine collection.
- Please refer to the Specimen Collection Manual for instructions on 24 Hour Urine Collection:
Specimen Collection Criteria
Collect (preferred specimen): 24 hour urine sample with 15 mL of 6N Hydrochloric Acid added prior to the start of collection.
Also acceptable [if collected with other tests (Stone Former)]: 24 hour urine collection with no preservative, acidified in the Laboratory upon receipt.
- Keep 24 hour urine specimen iced or refrigerated during collection.
- Include start and end dates and times for the collection period on the specimen container.
Urine Preservative Options
6N Hydrochloric Acid
Boric Acid (10g)
50% Acetic Acid
Preparation for Courier Transport
Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.
- Random urine specimens.
- Samples not kept refrigerated (2-8°C or 36-46°F).
- Samples not collected and processed as indicated.
Measure total volume of 24 hour urine specimen. Record total volume and collection start and end dates and times in the LIS system. Aliquot a minimum of 10 mL from the well-mixed 24 hour urine collection. The pH of 24-hour urine collection with added preservative should be 4.0 or lower. Adjust the pH of the aliquot to between 1.0 and 3.0. The specimen will be heated to 56°C for 15 minutes in Chemistry during sample processing, prior to storage. Refrigerate aliquot prior to analysis. the sample will, again, be heated to 56°C in Special Testing, prior to analysis, to re-dissolve the oxalate.
Specimen Stability for Testing:
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 21 days
Frozen (-20°C/-4°F or below): 21 days
Specimen Storage in Department Prior to Disposal:
Refrigerated (2-8°C or 36-46°F): 7 days
Royal Oak Special Testing Laboratory
Varies, once per week.
Results available within 7 days.
Adult Males: 7-44 mg/24 hours.
Adult Females: 4-31 mg/24 hours.
Children: 13-38 mg/24 hours.
Enzymatic using oxalate oxidase.
Oxalate in urine may arise either as an end-product of intermediary metabolism or from dietary sources. Decreased oxalate excretion is associated with hyperglycemia and hyperglycinuria. Increased excretion of oxalate is attributed to increased (1) ingestion of oxalate precursors or oxalate rich foods (2) formation of oxalate as in primary hyperoxaluria and (3) absorption of oxalate in a number of gastrointestinal disorders that produce severe fat malabsorption. Formation of the sparingly soluble calcium salt of oxalate in the urinary tract is considered the major factor in urolithiasis (stone formation).
Excessive amounts of oxalate rich foods or Vitamin C (exceeding 16 mmol/L) can interfere with the assay and should be avoided 48 hours prior to urine collection.
Urinary oxalate is useful in assessing the risk of renal calcium stone formation (urolithiasis) and is determined as part of the Stone Former Panel.
LOINC: 2701-1, 27222-9
Special Chemistry Laboratory – RO
Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.