Glycosaminoglycans Detected in Dried Urine Samples

Almost all patients with mucopolysaccharidoses (MPS) have increased levels of glycosaminoglycans (GAGs) in their urine, but transportation of liquid samples may be challenging.

As transportation of liquid urine samples in appropriate conditions for long distances, especially across international borders, could be difficult, urine samples dried onto filter paper could be a solution to the problem.

Scientists at the Portal Hospital de Clinicas (Porto Alegre, RS, Brazil) collected urine samples from untreated MPS patients and from healthy controls. Dried-urine filter paper (DUFP) were prepared with four rectangles measuring 15×40 mm of filter paper which were then completely dipped into the urine flasks for a few seconds and then dried at room temperature for at least four hours. A colorimetric method for total urinary GAG quantification was used with slight modification and is based in the reaction of GAGs with dimethylmethylene blue.

The scientists found that there were no differences in the concentration of GAGs between urine and DUFP samples Concentration of GAGs in DUFP samples of MPS patients never overlapped with that of normal controls. Untreated patients with MPS and normal controls were well discriminated using any of the samples. Creatinine concentration in liquid urine and DUFP samples was also determined and used as a correction factor. The concentration of GAG was found to be almost identical in liquid and DUFP samples in all the controls.

The authors concluded that conclude that determination of GAGs on DUFPs is comparable to the ones performed in liquid urine samples. Their incorporation by reference laboratories would provide an additional screening tool, which could be useful in particular circumstances and which could be made available along with the existing methods of GAG analysis. Handling and mailing of filter paper samples will facilitate the identification of MPS patients worldwide, especially when samples need to travel long distances and cross international borders, contributing to the earlier diagnosis and timely treatment of these diseases.

The mucopolysaccharidoses (MPS) are inherited metabolic disorders with bone, joint, and visceral abnormalities, leading to multiorgan dysfunction and, sometimes, neurological manifestations. The study was published in the January 2013 edition of the journal Clinica Chimica Acta.

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Portal Hospital de Clinicas