Hurler-like phenotype: Enzymatic diagnosis in dried blood spots on filter paper

Background: Clinical differentiation among mucopolysaccharidosis, oligosacc haridosis, and mucolipidosis II and III is difficult. We describe methods f or the assay of 8 lysosomal enzymes in dried blood spots on filter paper th at allow screening for 12 lysosomal storage diseases that present with a Hu rler-like phenotype. Methods: To test tubes containing 3-mm blood spots, we added elution liquid and fluorescent or radioactive substrate solution. After incubation at 37 degreesC, the reaction was terminated by the addition of a stop buffer. The amount of hydrolyzed product was compared with a calibrator to allow the q uantification of enzyme activity. Sample stability was studied during stora ge for 21 days and during shipment of samples. We measured enzyme activitie s in 85 healthy controls (35 newborn, 50 adult), 57 patients suffering from 11 lysosomal storage diseases, and 46 obligate carriers. Results: Intra- and interassay CVs were <9% and < 15%, respectively. Mean a ctivity losses during transportation or storage for up to 21 days at 4 degr eesC were less than or equal to 27%. Enzyme activities in all patients were outside the ranges of values seen for carriers and controls. Conclusions: The described methodology distinguishes between patients and c ontrols with samples that are sufficiently stable to be mailed to the testi ng laboratory. (C) 2001 American Association for Clinical Chemistry.