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Creatine Biosynthesis Disorders Panel, Urine
Test Code94600
CPT Codes
82540, 82570, 82542
Includes
Guanidinoacetate, Creatine, Creatinine, Creatine/Creatinine
Preferred Specimen
1 mL random urine collected in a sterile, leak-proof container
Minimum Volume
0.15 mL
Other Acceptable Specimens
24-hour urine collected in a sterile, leak-proof container
Instructions
Collect a random urine specimen. Immediately freeze specimen. Correct specimen collection and handling is crucial to achieve reliable results.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 28 days
Refrigerated: Unacceptable
Frozen: 28 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Specimens other than urine • Specimens not frozen immediately after collection
Methodology
Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS)
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Set up: Tues; Report available: 4 days
Reference Range
See Laboratory Report
Clinical Significance
The intended use for this test is as a means of evaluating patients with a suspected inherited disorder of creatine metabolism. The cerebral creatine deficiency syndromes (CCDS), inborn errors of creatine metabolism, include the two creatine biosynthesis disorders (guanidinoacetate methyltransferase [GAMT] deficiency and L-arginine: glycine amidinotransferase [AGAT or GATM] deficiency), and the X-linked creatine transporter [SLC6A8] deficiency. Intellectual disability and seizures are common to all three CCDS. The majority of individuals with GAMT deficiency have a behavior disorder that can include autistic behaviors and self-mutilation; a significant proportion have pyramidal/ extrapyramidal findings. Onset is between the ages of three months and three years. The phenotype of SLC6A8 deficiency in affected males ranges from mild intellectual disability and speech delay to severe intellectual disability, seizures, and behavior disorder, with age at diagnosis ranging from 2 to 66 years. Females heterozygous for SLC6A8 deficiency may have learning and behavior problems.
