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Test Code POXA1 Oxalate, Plasma

Reporting Name

Oxalate, Plasma

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Assessing the body pool size of oxalate in patients with enzyme deficiencies, such as primary hyperoxaluria (PH),  or patients with enteric hyperoxaluria (EH)


Aiding in the diagnosis of PH in a patient with chronic kidney disease (CKD) of indeterminate cause when urinary oxalate is not available


Monitoring patients with renal failure and primary or enteric hyperoxaluria in order to be sure they are receiving enough dialysis


Aiding in maintaining plasma oxalate levels below supersaturation (25-30 mcmol/L)

Method Name


Specimen Required

Any client who has never collected a specimen for this test should call 800-533-1710 or 507-266-5700 and ask for the Clinical Specialty Laboratory for more detailed instructions.


Patient Preparation:

1. Fasting (12 hours)

2. Patient should avoid taking vitamin C supplements for 24 hours prior to collection.

Specimen Type: Acidified plasma

Collection Container/Tube: Green top (sodium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 5 mL

Collection Instructions:

1. Place specimen on wet ice immediately.

2. Centrifuge for 10 minutes at 3,500 rpm at 4° C within 1 hour of collection.

3. Aliquot plasma into a plastic vial.

4. Adjust the pH of the plasma specimen to a pH of 2.3-2.7 with approximately 10 mcL concentrated (12M) hydrochloric acid (or 20 mcL of 6M HCl) per 1 mL plasma.

Additional Information: Nonacidified specimens can be accepted if the heparinized plasma is properly frozen. However, a disclaimer will be added in nonacidified plasma: Sample was received nonacidified and frozen. In nonacidified samples oxalate values may increase spontaneously.

Specimen Type

Plasma Na Heparin

Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Heparin Frozen 30 days

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

≤2.0 mcmol/L

Reference values have not been established for patients under 18 years old or greater than 87 years of age.


In patients with normal renal function, the presence of increased plasma oxalate concentration is good evidence for overproduction of oxalate (primary hyperoxaluria: PH).


In the presence of renal insufficiency, plasma oxalate levels can be markedly elevated in patients with PH or enteric hyperoxaluria (EH). Increased levels of plasma oxalate can be found in dialysis patients without EH or PH, but the degree of elevation is less.(1)


In patients with possible primary hyperoxaluria and renal insufficiency, the diagnosis often can be presumptively made by knowing the plasma level of oxalate. However, ancillary tests, such as the demonstration of oxalate crystals in tissues (other than the kidney) or increased glycolate in dialysate (for patients on dialysis) are frequently necessary to make an accurate diagnosis.

Day(s) and Time(s) Performed

Monday through Friday; 7:30 a.m.-5 p.m.

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 U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
POXA1 Oxalate, Plasma 15085-4


Result ID Test Result Name Result LOINC Value
POXA1 Oxalate, Plasma 15085-4

Special Instructions


If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Testing Algorithm

See Hyperoxaluria Diagnostic Algorithm in Special Instructions.