This test measures the activity of enzymes associated with 6 lysosomal storage disorders (LSDs) as well as C20, C22, C24, and C26 lysophosphatidylcholine (LPC) species in DBS by tandem mass spectrometry. The 6 enzymes are deficient or absent in Gaucher, Niemann-Pick A/B, Pompe, Krabbe, Fabry disease, or mucopolysaccharidosis I (MPS I). Long chain (C24 and C26) LPC species are elevated in patients with peroxisomal disorders such as X-linked adrenoleukodystrophy (X-ALD) and peroxisomal biogenesis disorders. LPCBS / Lysophosphatidylcholines by Liquid Chromatography Tandem Mass Spectrometry (Reflex), Blood Spot also measures LPC species in dried blood spots by tandem mass spectrometry and serves as a second-tier method to this assay. Samples with abnormal concentrations of lysophosphatidylcholines as measured using this assay will be reinjected and analyzed using LPCBS / Lysophosphatidylcholines by Liquid Chromatography Tandem Mass Spectrometry (Reflex), Blood Spot.
Two 1/8" dried blood spots are excised from a single specimen and placed into individual microtiter plates. One spot is treated with Perkin Elmer 6-Plex Mix containing substrate and internal standard for acid sphingomyelinase (ASM), beta-glucocerebrosidase (ABG), alpha-glucosidase (GAA), alpha-galactosidase (GLA), galactocerebrosidase (GALC), and alpha-L-iduronidase (IDUA) is added. The enzyme plate is sealed and incubated for 18 hours (+ or -2 hours). Following the incubation the enzyme plate is purified by liquid-liquid extraction. The second dried blood spot is extracted with methanol containing d4-C26 LPC on day 2 of the procedure. The extracts are evaporated and reconstituted in the prepared LPC plate and analyzed by tandem mass spectrometry.(Unpublished Mayo method)