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Test ID: I2SBS Iduronate-2-Sulfatase, Blood Spot

Useful For

Diagnosis of mucopolysaccharidosis II (MPS II, Hunter syndrome) using dried blood spot specimens


This test is not useful for determining carrier status for MPS II.

Reporting Name

Iduronate-2-sulfatase, BS

Specimen Type

Whole blood

Necessary Information

Provide a reason for testing with each specimen.

Specimen Required

Supplies: Card-Blood Spot Collection (Filter Paper) (T493)


Preferred: Blood spot collection card

Acceptable: PerkinElmer 226 (formerly Ahlstrom 226) filter paper, Munktell TFN, and Whatman Protein Saver 903 paper

Specimen Volume: 2 Blood spots

Collection Instructions:

1. An alternative blood collection option for a patient 1 year of age or older is a fingerstick. See How to Collect Dried Blood Spot Samples via fingerstick.

2. Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry.

Additional Information:

1. For collection instructions, see Blood Spot Collection Instructions

2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777)

3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800)

Specimen Minimum Volume

1 Blood spot

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 90 days FILTER PAPER
  Frozen  90 days FILTER PAPER
  Refrigerated  90 days FILTER PAPER

Clinical Information

The mucopolysaccharidoses are a group of 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 GAG in the lysosomes interferes with normal functioning of cells, tissues, and organs. Mucopolysaccharidosis II, (MPS II, Hunter syndrome) is an X-linked lysosomal storage disorder caused by the deficiency of iduronate sulfatase (IDS) enzyme and gives rise to the physical manifestations of the disease.


Clinical features and severity of symptoms are widely variable ranging from severe infantile onset disease to an attenuated form, which generally has a later onset with a milder clinical presentation. Symptoms may include coarse facies, short stature, enlarged liver and spleen, hoarse voice, stiff joints, cardiac disease, and profound neurologic involvement leading to developmental delays and regression. As an X-linked disorder, MPS II occurs primarily in male patients with an estimated incidence of 1 in 120,000 male births, although symptomatic carrier females have been reported. Treatment availability, including hematopoietic stem cell transplantation and enzyme replacement therapy, makes early diagnosis desirable, as early initiation of treatment has been shown to improve clinical outcomes. Newborn screening for MPS II has been implemented in some states.


A diagnostic workup in an individual with MPS II typically demonstrates elevated levels of urinary GAG and increased amounts of both dermatan and heparan sulfate (see MPSQU / Mucopolysaccharides Quantitative, Random, Urine and MPSBS / Mucopolysaccharides, Blood Spot). Reduced or absent activity of IDS can confirm a diagnosis of MPS II but may also be deficient in unaffected individuals with pseudodeficiency as well as individuals with multiple sulfatase deficiency. Enzymatic testing is not reliable to detect carriers. Molecular genetic testing of the IDS gene allows for detection of the disease-causing variant in affected patients and subsequent carrier detection in female relatives (see MPS2Z / Hunter Syndrome, Full Gene Analysis, Varies). Currently, no clear genotype-phenotype correlations have been established.(1)

Reference Values

≥1.5 nmol/hour/mL


Results below 1.5 nmol/hour/mL in properly submitted specimens are consistent with iduronate-2-sulfatase deficiency (mucopolysaccharidosis II: MPS II, Hunter syndrome). If clinically indicated, consider further confirmation by molecular genetic analysis of the IDS gene. Note that this enzyme's activity can also be reduced in multiple sulfatase deficiency (MSD).(2) If clinically indicated, consider biochemical genetic testing of other sulfatases or molecular genetic testing of the SUMF1 gene to exclude MSD.


Normal results (≥1.5 nmol/hour/mL) are not consistent with iduronate-2-sulfatase deficiency.

Day(s) Performed


Report Available

8 to 15 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
I2SBS Iduronate-2-sulfatase, BS 79462-8


Result ID Test Result Name Result LOINC Value
61901 Iduronate-2-sulfatase, BS 79462-8
35209 Reviewed By 18771-6
35210 Interpretation (I2SBS) 59462-2

Method Name

Fluorometric Enzyme Assay

Clinical Reference

1. D'Avanzo F, Rigon L, Zanetti A, Tomanin R: Mucopolysaccharidosis type II: One hundred years of research, diagnosis, and treatment. Int J Mol Sci. 2020 Feb 13;21(4):1258. doi: 10.3390/ijms21041258

2. Hopwood JJ, Ballabio A: Multiple sulfatase deficiency and the nature of the sulfatase family. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed January 13, 2022. Available at

3. Neufeld EF, Muenzer J: The Mucopolysaccharidoses. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed January 13, 2022. Available at

4. Scarpa M: Mucopolysaccharidosis type II. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2007. Updated October 4, 2018. Accessed January 13, 2022. Available at


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:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602)

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: