OXA – ” Oxalate, Plasma”

This test will now be sent to MAYO. See bolded information for changes.

Patient Preparation: Patient should be fasting for at least 12 hours prior to collection. Patient should avoid taking vitamin C supplements for 24 hours prior to collection. 

Collect: Green sodium heparin 

Specimen Preparation: After drawing specimen, immediately place green sodium heparin tube on wet ice. Centrifuge for 10 minutes 3500 rpm within 1 hour of collection. Use of a 4 degree °C refrigerated centrifuge is optimal but not required. Aliquot 5.0 mL plasma in screw capped plastic vial. 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. CRITICAL FROZEN. 

Minimum Volume: 2.0 mL

Alternate Specimen: Nonacidified specimens can be accepted if the heparinized plasma is properly frozen. A disclaimer will be added in nonacidified plasma, “Sample was received nonacidified and frozen. In nonacidified samples oxalate values may increase spontaneously.” Although there can be a small absolute increase of plasma oxalate in nonacidified specimens, this will not change the clinical interpretation. 

Rejection Criteria: Sample collected in anything other than a green sodium heparin. 

Stability: Room temperature: Unacceptable
                Refrigerated: Unacceptable
                Frozen: 30 days

Methodology: Enzymatic

Reference Range: ≤ 2.0 mcmol/L
Reference values have not been established for patients younger than 18 years of age or older than 87 years of age. 

Turnaround Time: 5 – 9 days

Performed Days: Monday – Friday

Performing Laboratory: MAYO Clinic Laboratories