Quantitative GAG Analysis
MPS disorders are a group of lysosomal storage diseases with defects in enzymes needed for the degradation of glycosaminoglycans (GAGs). Eleven enzymes are involved in the catabolic pathways of chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), or hyaluronan. Deficiencies of these enzymes result in specific GAG accumulations in lysosomes and cellular dysfunction, ultimately leading to clinical manifestations.
Seven types of MPS disorders have been classified based on the enzymatic defects and storage material involved. MPS disorders are multi-systemic, with progressive involvement of the brain, visceral organs, and bones. Non-degraded or partially degraded fragments of GAGs are excreted in the urine and can be used for the screening and diagnosis of MPS disorders. Currently, the DMB dye-binding assay is used in clinical laboratories for measurement of total GAGs quantity. The qualitative GAGs fractionation assay, by either TLC or electrophoresis, can visually detect the abnormal HS, DS and keratan sulfate. However, sensitivity and specificity are poor.
Quantitative analysis of DS, HS and CS by liquid chromatography and tandem mass spectrometry (LC-MS/MS) provides a new way to screen and diagnose MPS disorders. Urinary GAGs are digested into specific disaccharide repeating units by methanolysis. The concentrations of GAGs represented by their specific disaccharides are measured by a liquid chromatography and tandem mass spectrometry (LC-MS/MS) method using deuterium labeled GAG internal standards. This assay accurately measures DS and CS from 0.2-400 µg/mL and HS from 1.0-400 µg/mL. Findings can be further confirmed by either enzyme analysis or molecular analysis of the relevant genes.
- Urine: 3-5 mL (random void) in a clean container without any preservatives. Minimum of 1 mL is required
- Ship overnight frozen on dry ice
- 5 days