Urine analysis of glucose tetrasaccharide by HPLC; a useful marker for the investigation of patients with Pompe and other glycogen storage diseases

A high performance liquid chromatography method, adapted from an established urinary sugars method, has been developed for the analysis of a tetraglucose oligomer (Glc₄) in urine. Pompe disease results from defects in the activity of lysosomal acid α-glucosidase (GAA) with patients typically excreting increased amounts of Glc₄. Rapid determination of GAA in dried blood spots is now possible. However, enzymatic analysis is unable to discriminate between patients with Pompe disease and those individuals harbouring pseudo deficiency mutations. This method was able to quantify Glc₄ levels in all patients analysed with an established diagnosis of Pompe disease, and all controls analysed had Glc₄ levels below the limit of detection for this method. Importantly the method was able to discriminate between an individual known to harbour a pseudo Pompe mutation and patients with Pompe disease, providing a useful supporting test to enzymatic analysis. Sequential measurement of urinary Glc₄ has been proposed to monitor the effects of enzyme replacement therapy (ERT). We observed a clear decrease in Glc₄ levels following commencement of treatment in three patients studied. Additionally, raised levels of Glc₄ were observed in patients with glycogen storage disease (GSD) type Ia and type III suggesting that this method may have applications in other GSDs.