MPS screening methods, the Berry spot and acid turbidity tests, cause a high incidence of false-negative results in sanfilippo and morquio syndromes.

Because of differences in the types and quantities of glycosaminoglycans (GAGs) in various mucopolysaccharidoses (MPSs), MPS screening tests, including the Berry spot and acid turbidity tests, are not specific or sensitive enough for the preliminary diagnosis of MPS. A false-negative result is common. We analyzed urine samples collected from 492 patients who were examined for inborn errors of metabolism using the Berry spot and acid turbidity (qualitative and quantitative) tests. Of those, 48 MPS patients (seven with MPS I, 17 with MPS II, nine with MPS III, 11 with MPS IV, and four with MPS VI) underwent preliminary differentiation between MPS types by two-dimensional electrophoresis (2D-EP), and were confirmed by enzymatic assay. Approximately 21.0% and 7.1% of the 492 samples showed positive reactions in the Berry spot and acid turbidity tests, respectively. Of these, a total of 35 samples with MPS types I, II, and VI showed strong positive reactions in both tests. Five patients with Sanfilippo (MPS III) and six patients with Morquio (IV) syndromes showed false-negative results in both tests. In our study, approximately 13.8% (68 in 492 samples) samples showed a positive reaction in the Berry spot test but a negative one in the acid turbidity test, for unknown reasons. The Berry spot and acid turbidity tests are used extensively for the preliminary diagnosis of MPS in Asia; however, the possibility of a misdiagnosis of MPS type III and IV with both tests should be kept in mind. For accurate diagnosis and confirmation of MPS, the 2D-EP method and enzymatic assay are recommended. They provide high sensitivity, specificity, and efficiency in diagnosing MPS.

Plasma free amino acids in Taiwan Chinese: the effect of age.

Values of plasma amino acids (AA) in Taiwan Chinese in different age groups were determined. AA analysis was performed by ion-exchange chromatography. The results correlated well with the reference values published by Shapira in 1989, indicating that plasma AA concentrations are not evidently affected by race and dietary habits. We also confirmed the effect of age on plasma free AA levels. More than two thirds of 35 amino acids showed statistically significant differences between age groups (p<0.05, one-way ANOVA test). Levels of taurine, hydroxyproline, threonine, serine, glutamic acid, proline, citrulline and alpha-amino-eta-butyric acid varied with age (p<0.01). Only a few AA, including alpha-amino-adipic acid, glycine, alanine, cystine, homocystine, isoleucine, tyrosine, gamma-aminobutyric acid and tryptophan, showed no statistically significant differences between the different age groups. When comparing the mean differences in individual AA among these three age groups using the post-hoc test, alanine, tyrosine, phenylalanine, glycine, glutamine, cystine, homocystine, isoleucine, gamma-aminobutyric acid and tryptophan appeared to be constant across all age groups. Glutamic acid and serine correlated significantly with age (p<0.05), with a definite decline in concentration from infancy to adulthood (r=0.396 and 0.243; p<0.01, respectively). We conclude that AA values are not evidently affected by race, but they do vary with age.