Urinary Glycosaminoglycans--A Marker for MPS

• Published in: Indian journal of clinical biochemistry 2014-12, Vol.29 (S1), p.S125
• Main Authors: Gaikwad, S.U, Dave, M.B, Chawla, P.K, Shetty, D, Dherai, A.J, Ashavaid, T.F
• Format: Article
• Language: English
• ISSN: 0970-1915

Mucopolysaccharidoses (MPS), a group of inherited lysosomal disorders are associated with defects in glycosaminoglycan (GAGs) metabolism. In addition to the characteristic clinical findings they may present with an increase in urinary GAGs excretion. The objective of the study was to optimize urinary GAGs estimation in a routine laboratory. We optimized and validated urinary GAG estimation using dimethylmethylene blue dye binding method. Age matched reference ranges were established in 145 healthy subjects ranging from neonates to adults. Subsequently screening test is being offered in our laboratory since October 2012. A detailed clinical history and a random urine sample is obtained from the suspected patients. The GAGs are reported as mg/mmol of creatinine and the results are interpreted with age matched reference ranges. Amongst healthy individuals GAG excretion decreases with an increase in age wherein children excrete at least more than 3 times the adult range (1.5-5.1 mg/mmole creat). Thirty patients with developmental delay, coarse facies, bone defects etc were referred for screening. The suspected patients ranged from 9 days--26 years. A variable increase (1.2-5.3 fold) in GAG excretion when compared with age matched reference range was seen 66% of patients. These patients were further referred for MPS enzyme assays for confirmation. Age matched reference ranges are required to interpret the GAG results. Excretion of GAG amongst MPS patients varies remarkably depending on the type and severity of the disease. GAG estimation is the first line screening test to rule out MPS and the screen positive patients need to be further worked up for specific enzyme analysis.