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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

Clinical Information

Maple syrup urine disease (MSUD) is an inborn error of metabolism caused by the deficiency of the branched-chain alpha-keto acid dehydrogenase (BCKDH) complex. The BCKDH complex is involved in the metabolism of the branched-chain amino acids (BCAA): isoleucine, leucine, and valine. MSUD can be divided into 5 phenotypes: classic, intermediate, intermittent, thiamine-responsive, and dihydrolipoyl dehydrogenase (E3)-deficient, depending on the clinical presentation and response to thiamin administration. Classic MSUD, 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 intellectual diabilities, 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 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 are 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.


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.

Report Available

3 to 5 days

Day(s) Performed

Monday through Friday

Clinical Reference

1. Chuang DT, Shih VE, Max Wynn RR. Maple syrup urine disease (Branched-chain ketoaciduria). In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA. eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw Hill; 2019. Accessed October 5, 2022.

2. Frazier DM, Allgeier C, Horner C, et al: Nutrition management guideline for maple syrup urine disease: an evidence- and consensus-based approach. Mol Genet Metab. 2014 Jul;112(3)210-217. doi: 10.1016/j.ymgme.2014.05.006

3. Strauss KA, Puffenberger EG, Morton DH: Maple syrup urine disease. In: RA Pagon, MP Adam, HH Ardinger, et al, eds. GeneReviews[Internet]. University of Washington, Seattle; 2006. Updated April 23, 2020. Accessed October 5, 2022. Available at

4. Diaz VM, Camarena C, de la Vega A, et al: Liver transplantation for classical maple syrup urine disease: Long-term follow-up. J Pediatr Gastroenterol Nutr. 2014 Nov;59(5):636-639. doi: 10.1097/MPG.0000000000000469

5. Blackburn PR, Gass JM, Vairo FPE, et al:. Maple syrup urine disease: mechanisms and management. Appl Clin Genet. 2017 Sep 6;10:57-66. doi: 10.2147/TACG.S125962

Method Name

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

Portions of this test are covered by patents held by Quest Diagnostics

Specimen Type


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

Patient Preparation: Fasting (overnight preferred, 4 hours minimum). Infants should be drawn just before next feeding (2-3 hours without total parenteral nutrition: TPN if possible).

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Lavender top (EDTA), plasma gel tube, or green top (lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Collect specimen and place on wet ice. Note: Thrombin-activated tubes should not be used for collection.

2. Centrifuge immediately or within 4 hours of collection if specimen is kept at refrigerated temperature.

3. Being careful to ensure that no buffy coat is transferred, aliquot plasma into a plastic vial and freeze.

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Frozen 14 days

Reference Values


≤23 months: 31-105 nmol/mL

2-17 years: 30-111 nmol/mL

≥18 years: 36-107 nmol/mL



≤23 months: 48-175 nmol/mL

2-17 years: 51-196 nmol/mL

≥18 years: 68-183 nmol/mL



≤23 months: 83-300 nmol/mL

2-17 years: 106-320 nmol/mL

≥18 years: 136-309 nmol/mL



≤23 months: <2 nmol/mL

2-17 years: <3 nmol/mL

≥18 years: <5 nmol/mL

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 US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
AAMSD Amino Acid, MSUD Panel, P 94566-7


Result ID Test Result Name Result LOINC Value
32446 Valine 94567-5
32447 Isoleucine 94568-3
32448 Leucine 94569-1
32449 Allo-isoleucine 94570-9
32450 Interpretation (AAMSD) 49247-0
Mayo Clinic Laboratories | Endocrinology Catalog Additional Information: