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Test Code KSQNU Keratan Sulfate Quantitative , Urine

Secondary ID

64712

Useful For

Monitoring the pharmacodynamic effects of enzyme replacement therapy for Morquio A (MPS IVA)

Method Name

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

Reporting Name

Keratan Sulfate Quantitative, U

Specimen Type

Urine


Necessary Information


Patient’s age is required.



Specimen Required


Supplies: Plastic, Urine Tubes, 10 mL (T068)

Specimen Volume: 1 mL

Collection Instructions:

1. Collect a random urine collection (early morning preferred).

2. Immediately freeze specimen.

3. Pediatric collection: If applicable, include pediatric volumes if different than above.


Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen 365 days

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Clinical Information

The mucopolysaccharidoses (MPS) 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 (glycosaminoglycans: GAG). Undegraded or partially degraded GAG (also called mucopolysaccharides) are stored in lysosomes and excreted in the urine. Accumulation of GAG in lysosomes interferes with normal functioning of cells, tissues, and organs resulting in the clinical features observed in MPS disorders. There are 11 known enzyme deficiencies that result in MPS.

 

Mucopolysaccharidosis IV (Morquio syndrome) is caused by defective degradation of keratan sulfate due to deficiency of either N-acetylgalactosamine 6-sulfatase in MPS IVA or of beta-galactosidase in MPS IVB. Keratan sulfate, and also chondroitin-6-sulfate in the case of MPS IVA, accumulates in the cells and the excess is excreted in the urine.

 

Common clinical features of Morquio A and B include short-trunk dwarfism, a skeletal (spondyloepiphyseal) dysplasia distinct from that in the other MPS, corneal clouding, dental anomalies, cardiac lesions, hepatomegaly, and normal intelligence. Severity varies widely in both types although, is generally thought to be more mild in Morquio B. Estimates of the incidence of MPS IVA syndrome range from 1 in 200,000 to 1 in 300,000 live births and of MPS IVB, about 1 in 250,000 live births.

 

Enzyme replacement therapy (ERT) is available for Morquio A; however, for Morquio B, ERT is supportive only. ERT has been shown to decrease the level of keratan sulfate in the urine in Morquio A patients; however, correlation to therapeutic efficacy remains controversial.

Reference Values

0-12 months: ≤2.50 mg/mmol creatinine

13-24 months: ≤2.00 mg/mmol creatinine

25 months-4 years: ≤1.50 mg/mmol creatinine

5-10 years: ≤1.00 mg/mmol creatinine

11-18 years: ≤0.80 mg/mmol creatinine

>18 years: ≤ 0.50 mg/mmol creatinine

Interpretation

A single numeric value is reported.

 

Patient outcomes cannot be correlated to levels of urinary keratan sulfate.

Clinical Reference

1. Neufeld EF, Muenzer J: The Mucopolysaccharidoses. In The Online metabolic and Molecular Bases of Inherited Disease. Edited by D Valle, AL Beaudet, B Vogelstein B, et al. New York, NY, McGraw-Hill, 2014. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&Sectionid=62642135

2. Tomatsu S, Sawamoto K, Shimada T, et al: Enzyme replacement therapy for treating mucopolysaccharidosis type IVA (Morquio A syndrome): effect and limitations. Expert opinion on orphan drugs 2015;3(11):1279-1290 doi:10.1517/21678707.2015.1086640

Day(s) and Time(s) Performed

Varies

Analytic Time

10 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

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

82542

LOINC Code Information

Test ID Test Order Name Order LOINC Value
KSQNU Keratan Sulfate Quantitative, U In Process

 

Result ID Test Result Name Result LOINC Value
64712 Keratan Sulfate Quantitative, U In Process