Prader-Willi/Angelman Methylation
Test Mnemonic
PRADER
CPT Codes
- 81331 - QTY (1)
Aliases
- Angelman Syndrome Methylation
Performing Laboratory
ARUP
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 3 mL | Whole blood | ACD A or B (Yellow) | Refrigerated |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 3 mL | Whole blood | EDTA (Lavender) | Refrigerated |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1.5 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Refrigerated | 1 week |
| Ambient | 72 hours |
| Frozen | 1 month |
Days Performed
Mon, Thu
Turnaround Time
8 - 11 days
Methodology
| Name | Description |
|---|---|
| Fluorescence Monitoring | |
| Methylation Sensitive Polymerase Chain Reaction |
Reference Range
Special Info
Counseling and informed consent are recommended for genetic testing. Plasma, serum and frozen specimens in glass collection tubes will be rejected. This test is New York DOH approved.
Clinical Info
Preferred initial diagnostic test for Angelman syndrome or Prader-Willi syndrome. Background information: Characteristics of Angelman Syndrome (AS): Developmental delays by 6-12 months of age, seizures, microcephaly, movement or balance disorder, minimal or absent speech, and a distinctive behavioral phenotype, which includes a happy demeanor with frequent laughter, hand flapping, and excitability. Prevalence: 1 in 15,000. Inheritance: Varies, depending on the molecular genetic mechanism. Cause: Absence of maternal expression of the UBE3A gene. Molecular Genetic Mechanisms: Microdeletions in the AS/PWS critical region (68%), UBE3A mutations (11%), paternal uniparental disomy of chromosome 15 (7%), imprinting center defects (3%), unbalanced chromosome translocation (< 1%), and unknown (10%). Methodology: Bisulfite conversion and PCR amplification to detect methylation using melting curve analysis. Clinical Sensitivity: 78%. Analytical Sensitivity and Specificity: 99%. Characteristics of Prader-Willi Syndrome (PWS): Neonatal hypotonia, hyperphagia, obesity, global developmental delay, mild intellectual disability, hypogonadism, and a distinctive behavioral phenotype, which includes temper tantrums, stubbornness, manipulative behavior, and obsessive-compulsive behavior. Prevalence: 1 in 15,000. Inheritance: Varies, depending on the molecular genetic mechanism. Cause: Absence of the paternally contributed PWS/AS critical region of chromosome 15q11.2-q13. Molecular Genetic Mechanisms: Microdeletions in the PWS/AS critical region (70-75%), maternal uniparental disomy of chromosome 15 (25-29%), imprinting center defect or balanced chromosome translocation (< 1%). Methodology: Bisulfite conversion and PCR amplification to detect methylation using melting curve analysis. Clinical Sensitivity: Over 99%. Analytical Sensitivity and Specificity: 99%
Clinical Limitation
Molecular mechanisms not affecting methylation patterns that may result in AS or PWS will not be assessed. Diagnostic errors can occur due to rare sequence variations.