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Test ID: CRDPU    
Creatine Disorders Panel, Urine

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

 

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/
Creatinine

< 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/
Creatinine

< 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

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