26336 Hexose Tetrasaccharide (LAB6422)

​Urine Hex4 Biomarker for Pompe Disease

​Hex4 Normalized; MS/MS Creatinine (mM); Interpretation; Lab Director Signature; Medical Director Signature

​The urine Hex4 assay is used to monitor patients with Pompe disease (GSD II) on enzyme replacement therapy. It is also useful for the diagnosis of Pompe disease when performed in conjunction with the blood acid alpha glucosidase enzyme assay.

​No preservatives.

Preprandial (before meals) or fasting samples are preferred to avoid dietary artifacts and enhance sensitivity.

Urine should be stored at -20°C and shipped frozen on dry ice. Sample may be kept at room temperature for up to 4 hours. After this time, keep sample cold at 4°C for up to 24 hours. Freeze if stored for longer than 24 hours before shipping. If transportation to lab is same day as collection, (local hospitals only) the sample must be transported at 4°C on an ice pack or frozen on dry ice.

​Hex4 may be elevated in a number of pathological and physiological conditions and is not specific to Pompe disease.

The test name, Hex4, refers to hexose tetrasaccharide. This test specifically targets one hexose tetrasaccharide: the glucose tetrasaccharide Glc-alpha1-6Glc-alpha1-4Glc-alpha1-4Glc known as Glc4, a biomarker of glycogen storage. Glc4 is separated by UPLC from other hexose tetrasaccharides (Hex4) in urine and quantified by stable isotope dilution. The reported Hex4 value is a measure of Glc4. Concentrations are compared with age-matched control ranges. The profile is interpreted by an ABMGG board-certified laboratory director.

Background information: Glc4 is a limit dextrin produced by the amylolytic digestion of glucose polymers and is found in the urine and plasma of normal individuals. Its excretion may be mildly increased by ingestion of starch, glycogen (meat) and physical activity. In addition to the dietary origin, Glc4 may also be derived from glycogen released into the circulation from tissues (due to tissue damage/turnover) and acted upon by amylase and alpha-glucosidase activity (such as the ubiquitous glucosidase C) in the circulation. Glc4 has been found to be elevated in a number of pathological conditions including GSD II (acid alpha glucosidase deficiency), GSD III (debranching enzyme deficiency), GSD VI (liver phosphorylase deficiency), GSD IX (phosphorylase kinase deficiency), certain malignancies, acute pancreatitis and muscular diseases including Duchene muscular dystrophy.

High priority may be given to samples from known patients or a patient suspected to have a metabolic disorder based upon a Genetics consult (pager 970-2200).