Mucopolysaccharidoses, a group of inherited disorders are associated with defects in glycosaminoglycan metabolism. Thus, assessment of urinary glycosaminoglycan is used as a screening test for mucopolysaccharidoses. The detection methods range from qualitative spot tests to quantification using metachromatic dyes. In our laboratory we optimized a spectrophotometric quantitative method using a metachromatic dye, dimethylmethylene blue. Heparan sulfate was used for quantification. The glycosaminoglycan-dye complex showed a marked shift in color with increase in concentration. The color complex was quantified at 520 nm. The method was linear from 10-89 mg/L. An age matched normal range was obtained in 177 healthy individuals, grouped in 8 different age groups from neonates to adults. Urinary glycosaminoglycan concentration varied distinctly amongst the study population wherein the lowest range in healthy neonates was more than 3 times the upper limit of healthy adults. Urine samples from 10 patients with mucopolysaccharidoses were also included in the study for clinical validation. The method qualified both analytical and clinical validation and was found to be simple, robust and ideal to be offered as a screening test for mucopplysaccharidoses in a routine clinical chemistry laboratory.
Keywords: 1,9-Dimethymethylene blue; Age matched reference range; Glycosaminoglycan; Mucopolysaccharidoses.