[Studies on the modified dimethylmethylene-blue (DMB) method for determining glycosaminoglycans (GAG) in urine]

The measurement of glycosaminoglycans (GAG) in urine is very important because GAG is an essential constituent of urinary diseases. Since previously reported methods of determination of GAG are quite complicated, dangerous or not stable, we developed a very simple and rapid method to estimate the content of GAG in urine using a microplate and microplate reader. An aliquot of diluted urine is mixed with a 1,9, dimethylmethylene blue (DMB) dye. The assay is based on the metachromatic shift in absorption maximum which occurs when sulfated glycosaminoglycans are added to the dye. The recovery of GAG is good. Other urinary compounds such as sugar, protein and blood did not influence the measurement of GAG. A good correlation was obtained between the modified DMB method and Blumenkrantz and Asboe-Hansen's method (r = 0.737, p < 0.001). The accuracy of this method makes it useful for screening urinary diseases.