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Test ID: AAMSD Amino Acids, Maple Syrup Urine Disease Panel, Plasma

Reporting Name

Amino Acid, MSUD Panel, P

Useful For

Follow-up of patients with maple syrup urine disease

 

Monitoring of dietary compliance for patients with maple syrup urine disease

Specimen Type

Plasma


Necessary Information


1. Patient's age is required.

2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.



Specimen Required


Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: EDTA, plasma gel, or lithium heparin

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Fasting (overnight preferred, 4 hours minimum). Infants should be drawn just before next feeding (2-3 hours without TPN if possible).

2. Centrifuge within 4 hours if specimen is stored at refrigerated temperature and aliquot plasma. Send plasma frozen.


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Frozen 14 days

Reference Values

ISOLEUCINE

≤23 months: 31-105 nmol/mL

2-17 years: 30-111 nmol/mL

≥18 years: 36-107 nmol/mL

 

LEUCINE

≤23 months: 48-175 nmol/mL

2-17 years: 51-196 nmol/mL

≥18 years: 68-183 nmol/mL

 

VALINE

≤23 months: 83-300 nmol/mL

2-17 years: 106-320 nmol/mL

≥18 years: 136-309 nmol/mL

 

ALLO-ISOLEUCINE

≤23 months: <2 nmol/mL

2-17 years: <3 nmol/mL

≥18 years: <5 nmol/mL

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82136

LOINC Code Information

Test ID Test Order Name Order LOINC Value
AAMSD Amino Acid, MSUD Panel, P In Process

 

Result ID Test Result Name Result LOINC Value
32446 Valine 20661-5
32447 Isoleucine 20648-2
32448 Leucine 20649-0
32449 Allo-isoleucine 22670-4
32450 Interpretation (AAMSD) 59462-2

Clinical Information

Maple syrup urine disease (MSUD) is an inborn error of metabolism caused by the deficiency of the branched-chain ketoacid dehydrogenase (BCKDH) complex. The BCKDH complex is involved in the metabolism of the branched-chain amino acids (BCAA): isoleucine (Ile), leucine (Leu), and valine (Val). MSUD patients can be divided into 5 phenotypes: classic, intermediate, intermittent, thiamine-responsive, and dihydrolipoyl dehydrogenase (E3)-deficient depending on the clinical presentation and response to thiamine administration. Classic MSUD which is the most common and most severe form, presents in the neonate with feeding intolerance, failure to thrive, vomiting, lethargy, and maple syrup odor to urine and cerumen. If untreated, it progresses to irreversible mental retardation, hyperactivity, failure to thrive, seizures, coma, cerebral edema, and possibly death.

 

Age of onset for individuals with variant forms of MSUD is variable and some have initial symptoms as early as 2 years of age. Symptoms include poor growth and feeding, irritability, and developmental delays. These patients can also experience severe metabolic intoxication and encephalopathy during periods of sufficient catabolic stress.

 

MSUD is a panethnic condition, but is most prevalent in the Old Order Mennonite community in Lancaster, Pennsylvania with an incidence there of 1:760 live births. The incidence of MSUD is approximately 1:185,000 live births in the general population.

 

Treatment of MSUD aims to normalize the concentration of BCAA by dietary restriction of these amino acids. Because BCAA belong to the essential amino acids, the dietary treatment requires frequent adjustment, which is accomplished by regular determination of BCAA and allo-isoleucine concentrations. Orthotopic liver transplantation has been used with success and is an effective therapy for MSUD.

Interpretation

The quantitative results of isoleucine, leucine, valine, and allo-isoleucine with age-dependent reference values are reported without added interpretation. When applicable, reports of abnormal results may contain an interpretation based on available clinical interpretation.

Clinical Reference

1. Scriver's The Online Metabolic and Molecular Bases of Inherited Disease (OMMBID). Part 8 Amino Acids.  Accessed July 6, 2016. Available at: http://ommbid.mhmedical.com/book.aspx?bookid=971

2. Chuang DT, Shih VE, Max Wynn RR: In Maple Syrup Urine Disease (Branched-Chain Ketoaciduria). Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York, NY, McGraw-Hill, 2014. Accessed July 6, 2016. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&Sectionid=62675436.

3. Strauss KA, Puffenberger EG, Morton DH:.In Maple Syrup Urine Disease. 1993-2016. Edited by RA Pagon, MP Adam, HH Ardinger. GeneReviews. University of Washington, Seattle, WA. Updated 2013 May 9. Available at: http://www.ncbi.nlm.nih.gov/books/NBK1319

Analytic Time

3 days (not reported on Saturday or Sunday)

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical