Short communicationMass screening test for mucopolysaccharidoses using the 1,9-dimethylmethylene blue method:: Positive interference from paper diapers
Introduction
The mucopolysaccharidoses (MPS) are a group of disorders caused by a deficiency in the lysosomal enzymes involved in the degradation of glycosaminoglycans (GAGs). The undegraded GAGs are stored in lysosomes and subsequently are excreted in the urine. Quantitative measurement of urinary GAGs is therefore available for diagnosis of the MPS. The clinical manifestations of the MPS are coarse facies, skeletal deformities, hepatosplenomegaly, joint stiffness and variable degrees of psychomotor developmental delay [1].
Bone marrow transplantation (BMT) has been proposed as a treatment for MPS, both to correct the bone marrow-derived cells in the recipient by replacement, and also to correct other cells which take up enzyme secreted by the bone marrow-derived cells, especially macrophages [2].
Mass screening for MPS in early infancy could provide a method for presymptomatic diagnosis, and it could realize early BMT, in which clinical outcome would be better than in BMT after clinical manifestation became apparent 3, 4, 5. We have proposed organizing mass screening for MPS in Japan and a pilot study is in progress in the Gifu Prefecture using the dimethylmethylene blue (DMB) method. In this study, we have observed new positive interference from paper diapers. We describe our findings in the pilot study of mass screening for MPS.
Section snippets
Collection of urine specimens
Urine samples were collected from 44 060 infants at 6 months of age. A plastic sheet was placed on the diaper and a piece of cotton was put on it. Such a diaper was attached to the infant and, after the cotton was dampened with urine, it was removed. The urine sample was squeezed from the cotton and was placed in a plastic bottle. It was returned by mail and stored at −20°C until assay. Informed consent was obtained from the parents of the infants studied.
Pilot study for mucopolysaccharidoses in the Gifu Prefecture
Over a three-year period from
Mass screening pilot study for MPS
We tested 44 060 infants at 6 months of age. With an upper cut-off limit of 400 mg of GAG/g of creatinine, 842 infants (1.9%) were positive. A second sample was requested for the positive individuals, of which 671 were re-tested: In the second screening, 27 cases were found to be positive and in the third screening using the CPC/carbazole method, all specimens were found to be negative (Table 1). To determine the range of GAG excretion in this population, we analyzed 10 000 samples obtained
Discussion
Although urine samples are useful for metabolic screening, they often contain various substances that interfere with the results of the test. In our mass screening study for MPS, it was found that a component of paper diapers, when mixed with urine, interferes with the DMB method, and this component was suggested to be acrylic acid polymer. Whitley et al. [10]found that heparin, a sulfated GAG, is highly reactive in the assay, while other drugs that are likely to be administered to infants
Acknowledgements
We thank Dr. A. Tanaka (Osaka City University) for technical advice, SANYOKASEI for providing crosslinked acrylic acid polymer sodium salt, and the Gifu Research Center for Public Health, for their cooperation. This study was supported in part by Grants-in-Aid for Scientific Research (08670869) from the Ministry of Education, Science, Sports and Culture of Japan and by a grant from the Ministry of Health and Welfare, Japan.
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