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Test ID: IDSWB Alpha-L-Iduronidase, Blood

Reporting Name

Alpha-L-Iduronidase, B

Useful For

Diagnosis of mucopolysaccharidosis I, Hurler, Scheie, and Hurler-Scheie syndromes in whole blood specimens

Specimen Type

Whole blood

Necessary Information

Provide a reason for referral with each specimen.

Specimen Required


Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD)

Specimen Volume: 2 mL

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Ambient (preferred) 7 days
  Refrigerated  7 days

Reference Values

≥1.0 nmol/hour/mL

An interpretive report will be provided.

Day(s) and Time(s) Performed


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


LOINC Code Information

Test ID Test Order Name Order LOINC Value
IDSWB Alpha-L-Iduronidase, B 24057-2


Result ID Test Result Name Result LOINC Value
32355 Reason for Referral 42349-1
32356 Alpha-L-Iduronidase 24057-2
32357 Interpretation 59462-2

Clinical Information

The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by the deficiency of any of the enzymes involved in the stepwise degradation of dermatan sulfate, heparan sulfate, keratan sulfate, or chondroitin sulfate, also known as glycosaminoglycans (GAG). Accumulation of GAGs in lysosomes interferes with normal functioning of cells, tissues, and organs. There are 11 known disorders that involve the accumulation of GAGs. MPS disorders involve multiple organ systems characterized by coarse facial features, cardiac abnormalities, organomegaly, intellectual disabilities, short stature, and skeletal abnormalities.


Mucopolysaccharidosis I (MPS I) is an autosomal recessive disorder caused by a reduced or absent activity of the enzyme alpha-L-iduronidase due to mutations in the IDUA gene. More than 100 mutations have been reported in individuals with MPS I. Deficiency of alpha-L-iduronidase can result in a wide range of phenotypes categorized into 3 syndromes: Hurler syndrome (MPS IH), Scheie syndrome (MPS IS), and Hurler-Scheie syndrome (MPS IH/S). Because these syndromes cannot be distinguished biochemically, they are also referred to as MPS I and attenuated MPS I.


Clinical features and severity of symptoms of MPS I are variable, ranging from severe disease to an attenuated form that generally presents at a later onset with a milder clinical presentation. In general, symptoms may include coarse facies, progressive dysostosis multiplex, hepatosplenomegaly, corneal clouding, hearing loss, intellectual disabilities or learning difficulties, and cardiac valvular disease. The incidence of MPS I is approximately 1 in 100,000 live births. Treatment options include hematopoietic stem cell transplantation and enzyme replacement therapy.


A diagnostic workup in an individual with MPS I typically demonstrates elevated levels of urinary GAG (MPSQN / Mucopolysaccharides [MPS], Quantitative, Urine) and increased amounts of both dermatan and heparan sulfate being detected (MPSSC / Mucopolysaccharides [MPS] Screen, Urine). Reduced or absent activity of alpha L-iduronidase can confirm a diagnosis of MPS I; however, enzymatic testing is not reliable for carrier detection. Molecular sequence analysis of the IDUA gene allows for detection of the disease-causing mutation in affected patients and subsequent carrier detection in relatives. To date, a clear genotype-phenotype correlation has not been established.


Specimens with results below 1.0 nmol/hour/mL in properly submitted specimens are consistent with alpha-L-iduronidase deficiency (mucopolysaccharidosis I). Further differentiation between Hurler, Scheie, and Hurler-Scheie is dependent upon the clinical findings.


Normal results (≥1.0 nmol/h/mL) are not consistent with alpha-L-iduronidase deficiency.

Clinical Reference

1. Neufeld EF, Muenzer J: The mucopolysaccharidoses. Chapter 136. In The Metabolic Basis of Inherited Disease. Eighth edition. Edited by D Valle, AL Beaudet, B Vogelstein. New York, McGraw-Hill Book Company. Accessed 1/25/2017. Available at:

2. Chamoles NA, Blanco M, Gaggioli D, Casentini C: Hurler-like phenotype: enzymatic diagnosis in dried blood spots on filter paper. Clin Chem 2001;47:2098-2102

3. Martins AM, Dualibi AP, Norato D, et al: Guidelines for the management of mucopolysaccharidosis type I. J Pediatr 2009 Oct:155(4 Suppl):S32-S46

4. Enns GM, Steiner RD, Cowan TM: Lysosomal disorders: mucopolysaccharidoses. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS Roth. McGraw-Hill, Medical Publishing Division, 2009, pp 721-730

5. Clarke LA. Mucopolysaccharidosis Type I. In GeneReviews. Edited by RA Pagon, MP Adam, HH Ardinger et al. University of Washington, Seattle. Updated 2016 Feb 11. 1993-2017. Available at

Analytic Time

8 days

Method Name

Fluorometric Enzyme Assay


1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) in Special Instructions.

3. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.

Testing Algorithm

See Newborn Screen Follow-up for Mucopolysaccharidosis Type I in Special Instructions.


For more information, see Newborn Screening Act Sheet Mucopolysaccharidosis Type I: Decreased Alpha-L-Iduronidase in Special Instructions.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: