False positive screen test for mucopolysaccharidoses in healthy female newborns

Abstract Background In total, 930 urine samples obtained on 2nd and 3rd day from birth have been analyzed for the early diagnosis of Mucopolysaccharidoses. Methods Dimethylmethylene blue (DMB) assay and one-dimensional electrophoresis were performed in all urine samples. Agarose gel electrophoresis, before and after treatment with chondroitinase ABCand heparinases, was used for a comprehensive characterization. Results Out of 930 urine samples 7 showed anomalous electrophoretic pattern; 5 of them had high GAG levels by DMB test. Atypical samples (n = 7) were analyzed by agarose gel electrophoresis. After enzymatic digestion, some slow bands were still visible. A second urine sample of the above 7 newborns was analyzed at the age of 1 month, demonstrating both a normal pattern and normal GAG levels. Additional urine and vaginal mucussamples from 10 term neonates with vaginal bleedingshowed the same electrophoretic pattern observed in the 7 false positive samples. Conclusions The altered electrophoretic pattern may be due to the presence of glycoproteins and not to specific GAGs, due to high levels of maternal hormones exposure during pregnancy. To our knowledge, this is the first time maternal estrogen hormones are proposed as a likely cause of false-positive urinary glycosaminoglycan screen test in healthy newborns.