Test ID: CRDPU
Creatine Disorders Panel, Urine
NY State Approved 
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluation of patients with a clinical suspicion of inborn errors of creatine metabolism including arginine:glycine amidinotransferase deficiency, guanidinoacetate methyltransferase deficiency, and creatine transporter (SLC6A8) defect
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Additional Tests Lists test(s) that are always performed, at an additional charge, with the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| 23466 | Creatine, (Bill Only), U | No | Yes |
| 23467 | Creatinine, (Bill Only), U | No | Yes |
| 23468 | Guanidinoacetate, (Bill Only), U | No | Yes |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
CRDPU/88697 Creatine Disorders Panel, Urine is a single test that carries the results for the panel. When the test is resulted, the following procedures are billed:
23466 Creatine, (Bill Only), Urine
23467 Creatinine, (Bill Only), Urine
23468 Guanidinoacetate, (Bill Only), Urine
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
Method Name A short description of the method used to perform the test
Liquid Chromatography-Tandem Mass Spectometry (LC-MS/MS)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Arginine:Glycine Amidinotransferase Deficiency (AGAT)
CrT1 defect
GAMT (Guanidinoacetate Methyltransferase) Deficiency
Guanidinoacetate Methyltransferase (GAMT) Deficiency
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.
Container/Tube: Plastic, 10-mL urine tube (Supply T068)
Specimen Volume: 1 mL
Collection Instructions:
1. Collect a random urine specimen.
2. Immediately freeze specimen.
Forms:
1. 1. 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.
2. 2. If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) 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.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Urine | Frozen | 7 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Disorders of creatine synthesis (deficiency of arginine:glycine amidinotransferase [AGAT] and guanidinoacetate methyltransferase [GAMT]) and the creatine transporter (SLC6A8) deficiency are collectively described as creatine deficiency syndromes (CDS). AGAT and GAMT deficiencies are inherited in an autosomal recessive manner, while the creatine transporter defect is X-linked. All 3 disorders result in a depletion of cerebral creatine and typically present with cognitive disability, speech and language delays, and seizures. Patients with GAMT and the creatine transporter deficiency exhibit behavioral problems and features of autism. Some female carriers for the creatine transporter deficiency have been reported with learning disabilities and behavioral problems.
Diagnosis is possible by measuring guanidinoacetate (GAA), creatine (Cr), and creatinine (Crn) in plasma and urine. The profiles are specific for each clinical entity. Patients with GAMT deficiency typically exhibit normal to low Cr, very elevated GAA, and low Crn. In patients with AGAT deficiency, normal to low Cr, low GAA, and normal to low Crn is observed. In comparison, elevated Cr, normal GAA, normal to low Crn, and an elevated Cr:Crn ratio characterize patients with creatine transporter defect.
Treatment with oral supplementation of creatine monohydrate is available and effective for the AGAT and GAMT deficiencies; it has not been shown to improve outcomes in individuals with the creatine transporter defect.
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.
Males
| Age | Creatinine (nmol/mL) | Guanidinoacetate (nmol/mL) | Creatine (nmol/mL) | Creatine/ |
| < or =31 days | 430-5240 | 9-210 | 12-2930 | 0.02-0.93 |
| 32 days-23 months | 313-9040 | 16-860 | 18-10490 | 0.02-2.49 |
| 2-4 years | 1140-12820 | 90-1260 | 200-9210 | 0.04-1.75 |
| 5-18 years | 1190-25270 | 40-1190 | 60-9530 | 0.01-0.96 |
| >18 years (male) | 3854-23340 | 30-710 | 7-470 | 0.00-0.04 |
Females
| Age | Creatinine (nmol/mL) | Guanidinoacetate (nmol/mL) | Creatine (nmol/mL) | Creatine/ |
| < or =31 days | 430-5240 | 9-210 | 12-2930 | 0.02-0.93 |
| 32 days-23 months | 313-9040 | 16-860 | 18-10490 | 0.02-2.49 |
| 2-4 years | 1140-12820 | 90-1260 | 200-9210 | 0.04-1.75 |
| 5-18 years | 1190-25270 | 40-1190 | 60-9530 | 0.01-0.96 |
| >18 years | 1540-18050 | 30-760 | 5-2810 | 0.00-0.46 |
Interpretation Provides information to assist in interpretation of the test results
Reports include concentrations of guanidinoacetate, creatine, and creatinine, and a calculated creatine:creatinine ratio. When no significant abnormalities are detected, a simple descriptive interpretation is provided. When abnormal results are detected, a detailed interpretation is given. This interpretation includes an overview of the results and their significance, a correlation to available clinical information, elements of differential diagnosis, and recommendations for additional biochemical testing.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Correct specimen collection and handling is crucial to achieve reliable results.
Creatine supplementation will cause falsely elevated results.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Sykut-Cegielska J, Gradowska W, Mercimek-Mahutoglu S, Stockler-Ipsiroglu S: Biochemical and clinical characteristics of creatine deficiency syndromes. Acta Biochim Pol 2004;51:875-882
2. Stromberger C, Bodamer OA, Stockler-Ipsiroglu S: Clinical characteristics and diagnostic clues in inborn errors of creatine metabolism. J Inherit Metab Dis 2003;26:299-308
3. Stockler S, Schultz PW, Salomons GS: Cerebral creatine deficiency syndromes: clinical aspects, treatment and pathophysiology. Subcell Biochem 2007;46:149-166
Method Description Describes how the test is performed and provides a method-specific reference
A random urine sample is combined with stable isotope-labeled internal standards and acetonitrile. After centrifugation, an aliquot of this diluted sample is analyzed by injection onto liquid chromatography columns that separate the analytes from the bulk of the stable isotope dilution in the positive electrospray selected reaction monitoring mode using the Applied Biosystems API 3000 LC-MC/MC System with Analyst Software.(Bodamer OA, Bloesch SM, Gregg AR, et al: Analysis of guanidinoacetate and creatine by isotope dilution electroscopy tandem mass spectrometry. Clin Chim Acta 2001;308:173-178; Cognat S, Cheillan D, Piraud M, et al: Determination of guanidinoacetate and creatine in urine and plasma by liquid chromatography-tandem mass spectrometry. Clin Chem 2004;50:1459-1461)
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.
Wednesday; 12 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
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.
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.
82540-Creatine
82570-Creatinine
83789-Guanidinoacetate
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 |
|---|---|---|
| 23383 | Creatine | 15046-6 |
| 23384 | Creatinine | 14683-7 |
| 23385 | Guanidinoacetate | In Process |
| 23268 | Creatine/Creatinine Ratio | 13484-1 |
| 23270 | Creatine Disorders Panel Interp | 59462-2 |
| 23272 | Reviewed By | N/A |
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