Test Id : POXA1
Oxalate, Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessing the body pool size of oxalate in patients with enzyme deficiencies, such as primary hyperoxaluria (PH), or patients with enteric hyperoxaluria
Aiding in the diagnosis of PH in a patient with chronic kidney disease 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)
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
Method Name
A short description of the method used to perform the test
Enzymatic
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Oxalate
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
Specimen Type
Describes the specimen type validated for testing
Plasma Na Heparin
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
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 (for a minimum of 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 3500 rpm within 1 hour of collection. Use of a 4 degrees C refrigerated centrifuge is optimal but not required.
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. 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.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
2 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Heparin | Frozen | 30 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessing the body pool size of oxalate in patients with enzyme deficiencies, such as primary hyperoxaluria (PH), or patients with enteric hyperoxaluria
Aiding in the diagnosis of PH in a patient with chronic kidney disease 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)
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Oxalate is an insoluble dicarboxylic acid, which is an end product of liver metabolism of glyoxalate and glycerate. Humans lack an enzyme to degrade oxalate, and thus it must be eliminated by the kidney.
Oxalate is a strong anion and tends to precipitate with calcium, especially in the urinary tract.
Consequently, about 75% of all kidney stones contain calcium oxalate in some proportion. In renal failure oxalate is retained in the body, and it can precipitate in tissues causing tissue toxicity, a condition called oxalosis.
In the absence of disease, up to 90% of the body pool of oxalate is produced by hepatic metabolism and the other 10% is provided by oxalate contained in various foods. However, in the presence of gastrointestinal diseases that cause fat malabsorption, the percentage of oxalate absorbed from food can be much greater. The oxalate content of fruits and vegetables is quite variable, some being quite high and others virtually zero.
Oxalate is freely filtered by the glomerulus. A smaller amount is also secreted in the proximal tubule. If the glomerular filtration rate (GFR) is decreased, oxalate begins to be retained in the body. However, in persons without primary hyperoxaluria (PH) or enteric hyperoxaluria (EH), plasma levels do not exceed the normal range until the GFR decreases below 10-20 mL/min/1.73 m(2).
Plasma oxalate concentration is a reflection of the body pool size. When the pool increases, oxalate may precipitate in tissues and cause toxicity. Plasma oxalate pool size can be increased in various situations:
Increased production and accumulation results from an abnormality in at least 3 different enzymes:
Alanine glyoxalate transferase is necessary for the conversion of glycolate to alanine. A deficiency or intracellular mistargeting of this hepatic enzyme results in increased oxalate production (primary hyperoxaluria type1).
Glycolate reductase/hydroxypyruvate reductase deficiency in the liver and elsewhere in the body results in increased glyceric acid formation, which leads to increased oxalate production (primary hyperoxaluria type 2).
A third type of PH was recently shown to be due to variants of HOGA1 that encodes the enzyme
4-hydroxy-2-oxaloglutarate aldolase that is found in hepatic mitochondria (primary hyperoxaluria type 3).
Increased oxalate load can be caused by increased absorption from the intestines after consuming large amounts of oxalate-rich foods such as rhubarb, spinach, or nuts.
Certain abnormalities of the gastrointestinal tract can cause fat malabsorption including short bowel syndromes, inflammatory bowel disease, gastric bypass for obesity, and pancreatic insufficiency. All of these gastrointestinal abnormalities result in increased oxalate absorption from the intestinal tract. This condition referred to as EH is due to saponification of calcium by fatty acids in the colon, which in turn frees up oxalate anions for absorption.
Decreased urinary oxalate excretion in chronic kidney disease (CKD) also causes oxalate retention in the body.
Management of patients with PH and renal failure is difficult. Intensive dialyses are undertaken in an attempt to keep plasma levels below the level at which supersaturation and crystallization can occur in body tissues such as heart and bones (called oxalosis).
PH is typically diagnosed by measuring oxalate levels in urine. However, as kidney function decreases, the renal excretion of oxalate also decreases. In such situations, plasma oxalate levels are often be informative. Although plasma oxalate increases in CKD patients without PH, values are much higher in those CKD patients who do have PH or EH. Plasma oxalate is often used to monitor these patients during critical periods in and around kidney transplantation, dialysis, or liver transplantation.
Oxalate concentration in dialysate fluid is a reflection of the oxalate removed during dialysis.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
< or =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.
Interpretation
Provides information to assist in interpretation of the test results
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.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
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).
Nonacidified 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.
Supportive Data
A difference in plasma oxalate results between the previous and current methods was observed; Overall the new results were 2.5% higher by Bland-Altman analysis (2.5%, y=0.7284x + 2.0093, R[2] = 0.9537). However, the new method detected significantly lower results for samples with a plasma oxalate concentration greater than 20 mcmol/L (Bland-Altman bias =-25.6%).
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Perinpam M, Enders FT, Mara KC, et al: Plasma oxalate in relation to eGFR in patients with primary hyperoxaluria, enteric hyperoxaluria and urinary stone disease. Clin Biochem. 2017 Dec;50(18):1014-1019
2. Edvardsson VO, Goldfarb DS, Lieske JC, et al: Hereditary causes of kidney stones and chronic kidney disease. Pediatr Nephrol. 2013 Oct;28(10):1923-1942
Method Description
Describes how the test is performed and provides a method-specific reference
This is an enzymatic method based on the reduction of oxalate by oxalate oxidase. The reaction releases hydrogen peroxide, which in the presence of peroxidase reacts with a dye to give a colored end point that is measured using a BioTek EPOCH plate spectrophotometer at 590 nm.(Package insert: Oxalate Kit. Trinity Biotech; V. 07/2016)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
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 US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
83945
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| POXA1 | Oxalate, Plasma | 15085-4 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| POXA1 | Oxalate, Plasma | 15085-4 |