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Glycosaminoglycans
Test CodeGAGS
Quest Code
30422
Alias/See Also
Glycosaminoglycans, Urine
GAGS
GAGS
CPT Codes
83864
Preferred Specimen
20 mL (pediatric 4 mL) random urine collected in a plastic, leak-proof container
Minimum Volume
10 mL (pediatric 2 mL)
Instructions
An early morning specimen is preferred. Freeze immediately.
Include the patient age with the requisition.
Include the patient age with the requisition.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 8 weeks
Refrigerated: Unacceptable
Frozen: 8 weeks
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Unfrozen specimens • Specimens outside of listed stability
Methodology
Colorimetric (1,9-Dimethyl-Methylene Blue) Dye Binding
FDA Status
The performance characteristics of the listed assay was validated by BioAgilytix Diagnostics. The US FDA has not approved or cleared this test. The results of this assay can be used for clinical diagnosis without FDA approval. BioAgilytix Diagnostics is a CLIA certified, CAP accredited laboratory for performing high complexity assays such as this one.
Setup Schedule
Set up: Varies; Report available: up to 7 business days
Report Available
7 Days
Reference Range
| 0-1 year | <36.0 mg/mmol |
| 2-3 years | <17.8 mg/mmol |
| 4-5 years | <14.8 mg/mmol |
| 6-11 years | <12.4 mg/mmol |
| 12-13 years | <9.5 mg/mmol |
| 14-17 years | <5.1 mg/mmol |
| >17 years | <3.1 mg/mmol |
Clinical Significance
The mucopolysaccharidoses (MPSs) are a family of inheritable disorders caused by deficiency of lysomal enzymes required to degrade mucopolysaccharides, also known as glycosaminoglycans (GAGs). The undegraded or partially degraded gags are stored in lysosomes and excreted in the urine. The quantity of excreted urinary gags is age-dependent. Infants secrete more GAGs than adults. Normal urine contains primarily chondroitin sulfate with small quantities of heparin sulfate and dermatan sulfate.
Once mucopolysaccharidoses is diagnosed by total GAG analysis, a differential diagnosis based upon the abnormal distribution of sulfated GAGs in urine must be performed. Differential diagnosis is a requirement because many of the various enzyme deficiencies share similar clincal features. These features include a chronic and progressive course, multi-system involvement and organomegaly. Hearing, vision, cardiovascular function and joint mobility are affected. Profound mental retardation is found in the Hurler, Hunter and San Filippo syndromes (MPS types I, II and III), but normal intellectual functioning is retained in other MPSs and some mildly affected Hunter patients.
Once mucopolysaccharidoses is diagnosed by total GAG analysis, a differential diagnosis based upon the abnormal distribution of sulfated GAGs in urine must be performed. Differential diagnosis is a requirement because many of the various enzyme deficiencies share similar clincal features. These features include a chronic and progressive course, multi-system involvement and organomegaly. Hearing, vision, cardiovascular function and joint mobility are affected. Profound mental retardation is found in the Hurler, Hunter and San Filippo syndromes (MPS types I, II and III), but normal intellectual functioning is retained in other MPSs and some mildly affected Hunter patients.
Performing Laboratory
BioAgilytix Diagnostics
1320 Soldiers Field Rd
Brighton, MA 02135
Last Updated: September 17, 2019
