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BACKGROUND:Interest in lysosomal storage disorders, a collection of more than 40 inherited metabolic disorders, has increased because of new therapy options such as enzyme replacement, stem cell transplantation, and substrate reduction therapy. We developed a highthroughput protocol that simplifies analytical challenges such as complex sample preparation and potential interference from excess residual substrate associated with previously reported assays.

the introduction of MS/MS technology in Austria significantly increased the detection of inherited metabolic disorders that were previously not covered. A primary goal is the continuous effort by developing second-tier strategies with the inclusion of more specific markers in order to minimize the risk of false-negatives and to improve the positive predictive value of screening results. Early recognition of these disorders enables diagnosis and treatment before the onset of symptoms.

Lysozomal storage disorders are just beginning to be routinely screened using enzyme activity assays involving dried blood spots and tandem mass spectrometry (MS/MS). This paper discusses some of the analytical challenges associated with published assays including complex sample preparation and potential interference from excess residual substrate. Solutions to these challenges are presented in the form of on-line two-dimensional chromatography to eliminate off-line liquid-liquid extraction (LLE) and solid-phase extraction (SPE), the use of ultra-high-performance liquid chromatography (UHPLC) to separate excess substrate from all other analytes and multiplexed sample introduction for higher throughput required of a population screening assay. High sensitivity, specificity and throughput were demonstrated using this novel method.

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