MUCOPOLYSACCHARIDOSES SCREENING - DIMETHYLMETHYLENE BLUE VERSUS ALCIAN BLUE

The dimethylmethylene blue (DMB)-based screening procedure for mucopol ysaccharidosis1,2 and the alcian blue3 (AB)-based procedure both measu re glycosaminoglycan (GAG) content directly in urine. We compared the two procedures. Absorbance per microgram of GAG for DMB was 25 times t hat obtained with AB, resulting in a requirement for 10 times smaller sample volumes for the former. Recoveries of added heparan sulphate fo r the AB assay in the absence and presence of added protein (2.5 g/L) were comparable (78-95% and 75-111%), as was the case with the DMB ass ay. Here, recoveries were generally better (94-103% and 96-100%). The coefficient of correlation (CC) between the two methods measured on 86 reference urine samples was 0.861. For mucopolysaccharidosis urines t he CC was higher (0.928). Age-dependent reference values were comparab le. Performance of the assays was compared by measurement of GAG conte nt in 24 mucopolysaccharidosis urines. Standard deviation scores (meas ured value minus mean of reference values divided by standard deviatio n in reference values) and probabilities for classification in the pat ient group were calculated and compared. Especially for urines from pa tients with less distinctly increased GAG content (Sanfilippo, Scheie) , scores and probabilities were higher with the DMB assay.