Alanine:Glyoxylate Aminotransferase (AGXT) Mutation Analysis (G170R), Blood
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Identifying patients with the pyridoxine responsive form of PH1
Determining the presence of the Gly170Arg (G170R) mutation in the AGXT gene
Carrier testing of at-risk family members
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Detects Gly170Arg mutation associated with assessment of pyridoxine responsiveness only. This test is not diagnostic for hyperoxaluria type I.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Direct Mutation Analysis by Polymerase Chain Reaction (PCR)
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
AGXT Mutation Analysis (G170R)
PH1 (Primary Hyperoxaluria Type 1)
PH1 (Primary Hyperoxaluria Type 1)
Specimen Type Describes the specimen type needed for testing
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.
Specimen must arrive within 96 hours of draw.
Preferred: Lavender top (EDTA) or yellow top (ACD)
Acceptable: Any anticoagulant
Specimen Volume: 2 mL
1. Invert several times to mix blood.
2. Send specimen in original tube.
1. Molecular Genetics-Congenital Inherited Diseases Patient Information Sheet (Supply T521) in Special Instructions
2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
3. If not ordering electronically, submit a Molecular Genetics Request Form (Supply T245) with the specimen.
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.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder in which excessive oxalates are formed by the liver and excreted by the kidneys, causing a wide spectrum of disease ranging from renal failure in infancy to mere renal stones in late adulthood. It is caused by deficiencies of the liver-specific peroxisomal enzyme AGXT (alanine-glyoxylate amino-transferase). The diagnosis may be suspected when clinical signs, increased urinary oxalate, glycolate, and glycerate excretion are present. Diagnostic confirmation requires the enzyme assay of the liver tissue, although this test is not readily available.
The toxicity of excess oxalate has been implicated in disease pathogenesis. Thus, treatment options have primarily centered on limiting oxalate ingestion and absorption. Pyridoxine (vitamin B) has proven to be a promising therapeutic agent by increasing the concentration of cofactor involved in the metabolic reactions that decrease oxalate production. However, only 20% to 30% of patients have been known to be responsive to pyridoxine. Testing patients for pyridoxine responsiveness has been recommended at any stage of renal function, although assessment of pyridoxine responsiveness is not always easy to perform and diagnostic criteria have not been standardized. Recently, researchers at Mayo Clinic found that patients with a particular mutation (Gly170Arg) in the AGXT gene are responsive to the pyridoxine, while affected individuals without this mutation are not responsive.
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.
An interpretive report will be provided.
Reported as negative or positive. The laboratory provides an interpretation of the results. This interpretation includes an overview of the results and their significance and a correlation to available clinical information.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This assay will not detect all of the mutations that cause PH1. Therefore, the absence of a detectable mutation(s) does not rule out the possibility that an individual is a carrier of or affected with this disease.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
Rare polymorphisms exist that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing should be considered.
In rare cases, DNA alterations of undetermined significance may be identified.
A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.
Many disorders may present with symptoms similar to those associated with PH1. PH2, another type of primary hyperoxaluria, is not detected by this assay. Therefore, biochemical testing (HYOX/86213 Hyperoxaluria Panel, Urine) is recommended prior to DNA analysis to distinguish between these two disorders.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Milosevic D, Rinat C, Batinic D, Frishberg Y: Genetic analysis-a diagnostic tool for primary hyperoxaluria type I. Pediatr Nephrol 2002 Nov;17(11):896-898
2. Pirulli D, Marangella M, Amoroso A: Primary hyperoxaluria: genotype-phenotype correlation. J Nephrol 2003 Mar-Apr;16(2):297-309
3. Amoroso A, Pirulli D, Florian F, et al: AGXT gene mutations and their influence on clinical heterogeneity of type I primary hyperoxaluria. J Am Soc Nephrol 2001 Oct;12(10):2072-2079
Method Description Describes how the test is performed and provides a method-specific reference
A polymerase chain reaction (PCR)-based assay is used to detect the 630 G-A mutation (G170R) within exon 4 of the AGXT gene. Mutant and normal alleles are distinguished by digestion with the restriction enzyme Msp1. (Hahn S: 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.
Tuesday; 2 p.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
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 was developed and its performance characteristics 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 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.
81479-Unlisted molecular pathology procedure
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|
|22650||Reason For Referral||42349-1|