NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Assessing the body pool size of oxalate. The settings in which it has been most useful include patients with enzyme deficiencies, such as primary hyperoxaluria, which result in overproduction of oxalate.
In the presence of renal insufficiency, 3 uses of plasma oxalate are:
-In those patients with renal insufficiency from indeterminate causes and in whom the question of primary hyperoxaluria has arisen and urinary oxalate is not available, plasma oxalate has been used for diagnosis of primary hyperoxaluria
-Monitoring patients with renal failure who are thought to have primary hyperoxaluria
-As an aid to maintaining plasma oxalate at levels below that which supersaturation occurs
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Specimen Type Describes the specimen type needed for testing
Plasma Na Heparin
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Any client who has never drawn a specimen for this test should call 800-533-1710 or 507-266-5700 and ask for the Renal Laboratory for more detailed instructions.
Specimen Type: Acidified plasma
Collection Container/Tube: Green top (sodium heparin)
Submission Container/Tube: Plastic vial
Specimen Volume: 5 mL
1. Fasting (12 hours)
2. Place on wet ice immediately.
3. Centrifuge for 10 minutes at 3,500 rpm at 4 degrees C within 1 hour of draw.
4. Adjust the pH of the plasma specimen to a pH of 1 to 3.5 (ideal range is 2.3-2.7) with approximately 10 mcL concentrated (12N) HCl per 1 mL plasma.
1. Patient should avoid taking vitamin C supplements for 24 hours prior to draw.
2. Non-acidified specimen can be accepted if the heparinized plasma is properly frozen. However, in nonacidified plasma, oxalate values may increase spontaneously (average 50% increase for plasma oxalate <15 mcmol/L; average 10% increase for plasma oxalate >15 mcmol/L) and will be reported with a disclaimer.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Plasma Na Heparin||Frozen||7 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Oxalate is a dicarboxylic acid, which is an end-product of liver metabolism of glyoxalate and glycerate. Humans have no enzyme capable of degrading oxalate, which is quite insoluble, particularly when precipitated with calcium. Oxalate is important primarily because it affects kidney stone formation. About 85% of all kidney stones contain calcium oxalate in some proportion. Oxalate also may precipitate in tissues, causing tissue toxicity.
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 the oxalate in food. However, in the presence of gastrointestinal disease, the percentage absorbed from food can be much greater.
Oxalate is filtered by the glomerulus and efficiently secreted by the renal tubules. Once the glomerular filtration rate (GFR) begins to decrease, the pool size increases, but plasma levels do not increase out of the normal range until the GFR decreases to <10 mL/min to 20 mL/min.
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 2 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 I). Hepatic glycolate reductase/hydroxypyruvate reductase deficiency results in increased glyceric acid formation, which eventually leads to increased oxalate production (primary hyperoxaluria II).
-Pool size of oxalate can be increased by increased absorption from the intestine after consuming foods such as rhubarb, nuts, chocolate, or tea.
-Certain abnormalities of the gastrointestinal tract, including fat malabsorption, short bowel syndromes, and abnormal bile salt metabolism, all result in increased oxalate absorption from the intestinal tract.
-Increased pool size can result from decreased urinary excretion as occurs in chronic renal insufficiency.
Management of patients with primary hyperoxaluria and renal failure is difficult. Intensive dialyses are undertaken in an attempt to keep plasma levels below the level at which supersaturation is thought to occur.
Primary hyperoxaluria 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 may be informative. Plasma oxalate is often used to monitor these patients during critical periods in and around kidney transplantation, dialysis, or liver transplantation.
High value suggestive of primary hyperoxaluria. However if the patient has chronic kidney disease (GFR <30 mL/min/1.732m) plasma oxalate values up to 30 mcM/L can be normal.
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.
In nonacidified plasma specimens values near the reference range increase an average of 50% due to spontaneous oxalate generation.
In patients with normal renal function, the presence of increased plasma oxalate concentration is good evidence for overproduction of oxalate (primary hyperoxaluria).
In the presence of renal insufficiency, plasma oxalate levels are markedly elevated. Increased levels of plasma oxalate can be found in dialysis patients.
In patients with possible primary hyperoxaluria and renal insufficiency, the diagnosis often can be 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) often are 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).
For external clients only, non acidified specimens can be accepted if the heparinized plasma is promptly frozen. However, in nonacidified plasma oxalate values may increase spontaneously (average 50% increase for plasma oxalate <15 mcmol/L; average 10% increase for plasma oxalate >15 mcmol/L).
There is a difference (189%) between the new method (implemented June 2004) and the old method (R=0.9813; y=1.1975x + 1.901).
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Milliner DS, Eickholt JT, Bergstralh EJ, et al: Results of long-term treatment with orthophosphate and pyridoxine in patients with primary hyperoxaluria. N Engl J Med 1994;331:1553-1558
2. Kuiper JJ: Initial manifestation of primary hyperoxaluria type I in adults--recognition, diagnosis, and management. West J Med 1996;164:42-53
Method Description Describes how the test is performed and provides a method-specific reference
This is an enzymatic method based on 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 the Beckman Coulter DU800 Spectrophotometer. (Unpublished Mayo information)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 10 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) 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.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|