Urinary Screening of Mucopolysaccharidoses (MPS) in Cases Suspected of Inborn Errors of Metabolism Children in HUSM

Mucopolysaccharidoses (MPS) is a disease of inborn errors of metabolism (IEM). It constitutes a large and hetero- genous subgroup among the lysosomal storage diseases. For the detection of this disease, urinary glycosaminoglycan (GAG) is measured by dimethlmethylene blue (DMB) assay and high resolution electrophoresis (HRE) is done to characterize the different types of MPS. To screen for MPS in all urine samples suspected of inborn errors of metabolism sent to the metabolic laboratory from 1998 to 2008 and to look into the association between the positivity of DMB assay and HRE in the same sample, All urine samples sent to the metabolic laboratory that fulfilled the inclusion criteria were analyzed for GAG and were further subjected to HRE. Measurement of observed agreement using Cohen's kappa coefficient (k) was used for the association between both DMB and HRE method. A total of 134 urine samples were obtained however only 90 samples were analyzed. 28 (31.1%) of the samples had normal GAG levels, 59 (65.6%) had GAG levels between 1-2 folds above normal limits and 3 (3.3%) samples had more than 2 folds increment above the normal limits for age. Three samples showed abnormal bands when subjected to HRE. Poor association between both methods (k = 0.027) was observed. This study shows that all samples with high index of suspicion of MPS and elevated values of GAG of two folds or more should be subjected to HRE. Characterization of MPS through HRE gives the clinician some presumptive diagnosis and prognosis in managing these patients.