The spot test is not a reliable screening procedure for mucopolysaccharidoses.
To check the reliability of the Ames MPS paper spot test, which is based on the Azure A dye, we sent a series of urine samples to three laboratories where the spot test is part of the metabolic screening for mucopolysaccharidoses. In these laboratories false-negative results ranged between 19% and 35% and false-positive results ranged between 12% and 29% of all samples submitted. In contrast, the quantitative dimethylmethylene blue test (Clin Chem 1989;35:1472-7) detected an increased glycosaminoglycan content in all urine samples from mucopolysaccharidosis patients and gave no false-positive results. In the latter procedure, glycosaminoglycan content is expressed per millimole of creatinine, and age-dependent reference values are used. We conclude that the Ames spot test and other spot tests are unreliable as a screening procedure for mucopolysaccharidoses and should not be used to screen for these diseases.
de Jong
J G
JG
Institute of Neurology, University of Nijmegen, St. Radboud Hospital, The Netherlands.
Hasselman
J J
JJ
van Landeghem
A A
AA
Vader
H L
HL
Wevers
R A
RA
D001399:Azure Stains; D005188:False Negative Reactions; D005189:False Positive Reactions; D006025:Glycosaminoglycans / Q000652:urine*; D006801:Humans; D008751:Methylene Blue / Q000031:analogs & derivatives; D009083:Mucopolysaccharidoses / Q000175:diagnosis / Q000652:urine*; D011934:Reagent Strips; D015203:Reproducibility of Results
D001399:Azure Stains; D006025:Glycosaminoglycans; D011934:Reagent Strips; C025818:Azure A; D008751:Methylene Blue; C016401:1,9-dimethylmethylene blue