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Test ID: MSUSC Branched-Chain Amino Acids, Self-Collect, Blood Spot

Necessary Information

Patient's street address, city, state, ZIP (postal) code, country, and home phone are required (post-office [PO] boxes are not acceptable delivery locations).

Specimen Required

Supplies: Blood Spot Collection-Self Collect (T858)

Container/Tube: Blood Spot Self Collection Card

Specimen Volume: 2 Blood spots

Collection Instructions:

1. Order test each time the patient is to collect a dried blood specimen at home and mail the specimen directly to Mayo Clinic Laboratories.

2. Order should be placed a minimum of 3 days prior to desired date of collection.

3. Enter patient's address information for each order created, including street address (post-office [PO] boxes are not acceptable delivery locations), city, state abbreviation, ZIP (postal) code, country, and home phone number.

4. For each order, the Blood Spot Collection-Self Collect kit will be mailed directly to the patient for self-collection (delivery to a PO box will not occur).

5. See Dried Blood Spot Collection Tutorial for how to collect blood spots.

Useful For

Monitoring patients with maple syrup urine disease using specimens collected at home

Method Name

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

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

Reporting Name

Branched-Chain Amino Acids, SC, BS

Specimen Type

Whole blood

Specimen Minimum Volume

1 Blood spot

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 59 days FILTER PAPER
  Frozen  59 days FILTER PAPER
  Refrigerated  59 days FILTER PAPER

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). Classic MSUD 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 disability, hyperactivity, failure to thrive, seizures, coma, cerebral edema, and possibly death.


Treatment of MSUD aims to normalize the concentration of BCAA by dietary restriction of these amino acids. BCAA are essential amino acids that require frequent adjustment of the dietary treatment. Dietary monitoring is accomplished by regular determination of BCAA and Allo-Ile concentrations.

Reference Values

Allo-isoleucine: <2 nmol/mL

Leucine: 35-215 nmol/mL

Isoleucine: 13-130 nmol/mL

Valine: 51-325 nmol/mL


Quantitative results of allo-isoleucine, leucine, isoleucine, and valine with reference values are reported without added interpretation.

Clinical Reference

1. Morton DH, Strauss KA, Robinson DL, Puffenberger EG, Kelley RI: Diagnosis and treatment of maple syrup disease: a study of 36 patients. Pediatrics. 2002 Jun;109(6):999-1008. doi: 10.1542/peds.109.6.999

2. Strauss KA, Puffenberger EG, Carson VJ: Maple syrup urine disease. In: Adam MP, Ardinger HH, Pagon RA, et al. eds. GeneReviews [Internet]. University of Washington, Seattle; 2006. Updated April 23, 2020. Accessed June 21, 2022. Available at

Day(s) Performed

Monday through Friday

Report Available

2 to 4 days

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
MSUSC Branched-Chain Amino Acids, SC, BS 94571-7


Result ID Test Result Name Result LOINC Value
618731 Allo-isoleucine 94572-5
618732 Leucine 47679-6
618733 Isoleucine 47671-3
618734 Valine 47799-2
618730 Reviewed By 18771-6
BG775 Patient Street Address (No PO Box) 56799-0
BG776 Patient City 68997-6
BG777 Patient State 46499-0
BG778 Patient Zip Code 45401-7
BG779 Patient Country 77983-5
BG780 Patient Home Phone 42077-8
Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: