Evaluation of reliability for urine mucopolysaccharidosis screening by dimethylmethylene blue and Berry spot tests.
BACKGROUND
The mucopolysaccharidosis (MPS) are a group of inherited metabolic disorders resulting from the deficiency of the enzyme responsible for intralysosomal catabolism of glycosaminoglycans (GAGs). GAGs are progressively accumulated in multiple tissues and released into the corporal fluids. The first laboratory approximation to MPS diagnosis is the identification of an increased urinary GAG excretion. For this, several semiquantitative and quantitative methods have been developed. The aim of this retrospective statistical study was to evaluate the reliability of MPS urine screening for the semiquantitative Berry spot test (BST) and the quantitative dimethylmethylene blue test (DMB).


METHODS
The 24-h-urine samples (n = 246) were tested through BST, DMB, and for GAG excretion pattern by one-dimensional electrophoresis or thin layer chromatography.


RESULTS
the 204 samples that demonstrated a normal GAG excretion pattern were considered as non-MPS samples. Forty-two samples presented an abnormal GAG excretion pattern. Enzyme analysis was available for 31 out of 42 patients (31/42), confirming that all were affected by MPS. Urinary GAG concentrations of MPS patients by DMB were increased 1.04- to 7.1-folds, compared to age-related normal levels. The sensitivity was 100% for DMB and 93.6% for BST. DMB demonstrated a specificity of 74.5%, while BST a specificity of 53.9%. The specificity of MPS screening increased to 84.3%, considering conjunctly DMB and BST.


CONCLUSIONS
The DMB is a sensitive method, however, inclusion of BST could increase the specificity of MPS urine screening.
Mabe
Paulina
P
Unidad de Genética y Enfermedades Metabólicas, Instituto de Nutrición y Tecnología de los Alimentos (INTA), Universidad de Chile, Casilla 138-11, Santiago, Chile. pmabe@inta.cl
Valiente
Alf
A
Soto
Vivian
V
Cornejo
Verónica
V
Raimann
Erna
E
D002855:Chromatography, Thin Layer; D003124:Colorimetry; D015180:Electrophoresis, Gel, Two-Dimensional; D006025:Glycosaminoglycans / Q000652:urine*; D006801:Humans; D008751:Methylene Blue / Q000031:analogs & derivatives*; D009083:Mucopolysaccharidoses / Q000175:diagnosis* / Q000652:urine*; D015203:Reproducibility of Results; D012189:Retrospective Studies
D006025:Glycosaminoglycans; C435946:dimethylmethylene blue; D008751:Methylene Blue