Stability of urinary glycosaminoglycans in patients with mucopolysaccharidoses.

OBJECTIVE

The aim of this work is to investigate the degradation of urinary glycosaminoglycans (GAGs) at different storage temperatures, in order to identify whether frozen transportation to reference laboratories is necessary. An improved method for the determination of total GAGs with 1,9-dimethylmethylene blue (DMB) is presented.

DESIGN AND METHODS

Urine samples of 37 patients suffering from mucopolysaccharidoses (MPS) were analyzed in this study (13 Hunter, 6 Maroteaux-Lamy, 6 Morquio, 6 Sanfilippo, 5 Hurler-Scheie, and 1 Sly). Stability was assayed at room temperature, 5 degrees C and -30 degrees C, and analyses were repeated for at least 15 days. Spectrophotometric quantitation of GAGs with DMB was used for all determinations, using a variable wavelength for quantitation.

RESULTS

The concentration of urinary GAGs was stable for 10 days at room temperature, but it was found to be stable for more than 15 days at 5 degrees C and -30 degrees C.

CONCLUSIONS

The stability of GAGs allows urine samples to be sent for quantitation at a clinical laboratory without the need to freeze samples, as this would not affect results. This issue is important for the rapid detection of MPS at hospitals or primary health care centres, where GAGs determination is not performed.