Oxalate
| Label Mnemonic: | POXA |
| Epic code: | LAB8783 |
| Downtime form: | A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery |
Commercial Mailout Laboratory
6240-8 RCP
356-8593
6240-8 RCP
356-8593
Specimen(s):
Acidified Plasma
Specimen
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 degrees 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.
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 degrees 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.
Collection Medium:
 |
| Green top tube 4 mL (Na Heparin) |
Minimum:
Absolute Minimum: 2 mL Acidified plasma
Place on wet ice immediately.
Place on wet ice immediately.
Testing Schedule:
Monday through Friday; 7:30 a.m.-5 p.m.
Turn Around
Time:
3 days upon receipt at reference laboratory
Reference Range:
< or =2.0 mcmol/L
Reference values have not been established for patients under 18 years old or greater than 87 years of age.
Reference values have not been established for patients under 18 years old or greater than 87 years of age.
Interpretive Data:
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.
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.
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.
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.
Comments:
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)
Cautions:
Because increased production and decreased excretion rates of oxalate can increase the plasma oxalate concentration, the interpretation of any given plasma value must consider the patient's clinical setting.
Proper specimen processing and acidification are essential to obtain a quality result (see Specimen Required).
For external clients only, non-acidified specimens can be accepted if the heparinized plasma is promptly frozen. However, in nonacidified plasma specimens, plasma oxalate values near the reference range can increase up to 50% due to spontaneous oxalate generation.
Extremely high levels of ascorbic acid (vitamin C) in the blood interfere with testing. Due to this, patients should refrain from vitamin C supplements prior to collection.
Methodology:
Enzymatic
CPT Code:
83945