Clinics and Departments

Laboratory Services

Lab Dept:

Anatomic Pathology

Test Name:


General Information

Lab Order Codes:



Prader Willi/Angelman Syndrome Methylation Study; Methylation PCR Prader-Willi/Angelman Syndrome

CPT Codes:

81331 – SNRPN/UBE3A, methylation analysis

Test Includes:

Methylation-Sensitive Multiple Ligation-Dependent Probe Amplification (MLPA) with an interpretive report of findings.


Test Indications:

Confirmation of diagnosis in patients suspected of having either Prader-Willi or Angelman Syndrome based on clinical assessment or previous laboratory analysis.

Lab Testing Sections:

Anatomic Pathology - Sendouts

Referred to:

Mayo Medical Laboratories (MML: PWAS)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

14 – 21 days
Note: Specimens received Monday – Thursday will be processed for the run starting on the following Monday. Specimens received Friday – Sunday will be set up a week from the following Monday.

Special Instructions:

A “Molecular Genetics – Congenital Inherited Diseases Patient Information Sheet” (Mayo Supply T245) is required for all orders. An “Informed Consent Form for DNA Testing” (Mayo Supply T576) is available. Please contact the laboratory for forms.


Specimen Type:

Whole blood


Lavender top OR Yellow top ACD tube

Draw Volume:

3 mL (Minimum: 1 mL) blood

Processed Volume:

Same as Draw Volume


Routine venipuncture

Special Processing:

Lab Staff: Do Not centrifuge. Submit specimen in original vacutainer tube at room temperature. Specimen must reach Mayo within 96 hours of collection. Forward promptly.

Patient Preparation:


Sample Rejection:

Mislabeled or unlabeled specimens


Reference Range:

An interpretive report will be provided.

Critical Values:



The accuracy of the clinical assessment contributes to the likelihood of identifying a deletion or uniparental disomy. Rare cases of Prader-Willi Syndrome or Angelman Syndrome result from a subtle balanced translocation inherited from one of the parents. These may not be detected by this assay. A negative molecular test result, especially in the case of a clinical suspicion of Angelman Syndrome, does not rule out the diagnosis because point mutations may not be detected by these methods. Parental blood specimens may be requested if additional studies by polymerase chain reaction (PCR) are necessary to clarify the diagnosis.

In addition to disease-related probes, the MLPA technique utilizes probles localized to other chromosomal regions as internal controls. In certain circumstances, these control probes may detect other diseases or conditions for which this test was not specifically intended. Results of the control probes are not normally reported. However, in cases where clinically relevant information is identified, the ordering physician will be informed of the result and provided with recommendations for any appropriate follow-up testing.


Methylation-sensitive multiple ligation-dependent probe amplification (MLPA)


Mayo Medical Laboratories Web Page August 2015


1/13/2009: CPT updates
2/7/2013: CPT updates

  Lab Test Directory
    Microbiology/ Virology
    Other Fluids
    Transfusion Services

  Search Lab Test Directory
    List All Documents

  Lab Staff

  E-mail Lab Services