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Maple Syrup Urine Disease (MSUD) Mutation Analysis

CPT:

81205

MSUD occurs at an increased frequency in individuals of Ashkenazi Jewish descent and Mennonites, with a carrier frequency of 1 in 81. It is a metabolic disorder that, if untreated, results in intellectual disabilities, physical disabilities, coma and death.

Test Details

Synonyms

BCKD Deficiency; Branched-chain Ketoaciduria; Jewish Heritage Test; MSUD Carrier Testing, DNA;

 

Test Includes

Mutation(s) include: c.1312T>A (p.Y438N) (legacy name: Y438N (Y393N)); c.548G>C (p.R183P); c.832G>A (p.G278S); c.1114G>T (p.E372*) (legacy name: E372X (E422X))

Methodology

Polymerase chain reaction (PCR); primer extension; flow-sorted bead array analysis

Turnaround Time

10-14 days (when cell culture is required, add ~2 weeks) 

Pregnancy Week

0–13 Weeks
14–21 Weeks
22+ Weeks

Specimen Requirements

Specimen

Whole blood or mouthwash (see specimen kit for detailed instructions), amniotic fluid, chorionic villi.

Volume

Postnatal: 10 mL whole blood or mouthwash / Prenatal: 10mL amniotic fluid in orange-top polypropylene tube, 10-15 mg chorionic villi in laboratory provided screw-top tubes with sterile transport medium or one T-25 flask of confluent cells.

Container

Lavender-top (EDTA) tube or yellow-top (ACD-A) tube or mouthwash kit

Collection

Mouthwash collection:  Patient should not eat, drink, smoke or chew gum for at least one hour prior to collection. (See specimen kit for detailed instructions). 

Mouthwash samples can be sent when ordering up to two tests. When ordering more than two tests, blood samples are required.  10 mL of Scope® mouthwash that has been swished vigorously for at least 1 minute. Collect in orange-top 50 mL polypropylene tube. 

Special Instructions

Prenatal testing: Integrated Genetics clients should call 800-848-4436 to speak to a laboratory genetic coordinator before collecting any specimens.   In some circumstances, specimens from other family members may be required. 

All prenatal specimens (including cord blood) must be accompanied by a maternal blood or mouthwash specimen for analysis of possible maternal cell contamination. 

Discard first 2 mL; then 10 mL amniotic fluid in 15 mL orange-top polypropylene tube, 10-15 mg chorionic villi in laboratory-provided screw-top tubes with sterile transport medium or one T-25 flask of confluent cells. 

Additional sample must be obtained for back-up culture at one of our cytogenetics laboratories or another facility.  If additional testing is desired, more amniotic fluid is needed. For example, chromosome analysis requires an additional 15-25 mL (see Cytogenetics – Amniotic Fluid Chromosome Analysis test page) and AFAFP requires an additional 2 mL (see Amniotic Fluid Alpha-Fetoprotein - AFAFP test page).

Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; unlabeled or mislabeled specimen

Storage Instructions

Maintain specimen at room temperature

Additional Information

Couples who are planning a pregnancy or who are already pregnant may decide to have testing to find out if they are carriers and at risk of having a baby with MSUD. If both parents are found to be carriers, prenatal diagnosis by CVS or amniocentesis is available. Indications for MSUD testing include: Individuals with clinical characteristics of MSUD or family history of MSUD. Our MSUD analysis tests for 4 mutations for a 99% carrier detection rate in the Ashkenazi Jewish population.

Limitations

False positive or false negative results may occur for reasons that include: genetic variants, technical handling, blood transfusions, bone marrow transplantation, mislabeling of samples, or erroneous representation of family relationships.

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