Correlation of the levels of glycosaminoglycans between urine and dried urine in filter paper samples and their stability over time under different storage temperatures

Abstract

BackgroundMucopolysaccharidoses (MPSs) are a group of lysosomal storage diseases caused by the deficiency/absence of enzymes which catalyze the degradation of glycosaminoglycans (GAGs). The use of biological samples dried on filter paper has been increasing because it makes it easy to ship them to reference laboratories. Urinary GAGs are the main biomarkers of MPS and, thus, we studied the correlations of determinations to GAGs and creatinine, as well as compared the GAGs' profile on electrophoresis, between urine and dried urine in filter paper (DUFP) samples. We also assessed the GAG stability over time under different storage temperatures. MethodsWe quantified the GAG concentration in both sample types and compared the results by Pearson correlation. ResultsThe results were very similar, with r=0.97 for creatinine and with r=0.94 and r=0.98 for GAGs for controls and patients, respectively, with similar electrophoretic profiles. The GAG stability in DUFP was up to 30days at −20, 4, and 25°C and up to 21days at 37°C. ConclusionOur proposal assessed urinary GAGs in DUFP and concluded that these samples can be used in the investigation of MPS, replacing urine samples in neonatal screening and monitoring of therapies, due to ease of transportation and storage.