Ultra-performance liquid chromatography/tandem mass spectrometry for determination of sulfatides in dried blood spots from patients with metachromatic leukodystrophy

RATIONALE Metachromatic leukodystrophy (MLD) is a genetic autosomal recessive disease caused by a deficiency in arylsulfatase A. Accumulated sulfatides can be detected in the urine and detection of sulfatiduria is a useful test for diagnosis and monitoring. To our knowledge, no studies have explored the accumulation of sulfatides in dried blood spots (DBSs). We developed an ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) method for measuring sulfatides in DBSs from patients with MLD. METHODS DBSs were eluted with internal standard. After mixing and centrifugation, the organic layer was transferred to a 96-well microplate and dried, then resuspended in methanol/propanol solution. Samples were analyzed on an UPLC system. Total running time was 4 min. Quantification was achieved by multiple reaction monitoring using a tandem mass spectrometer. We evaluated the precision, linearity, and ion suppression of the method and analyzed sulfatide concentrations in DBS specimens from MLD patients (n = 9), pseudodeficiency (PD) patient (n = 1), obligate heterozygotes (OH) (n = 2) and normal controls (n = 124). RESULTS In negative-ion mode, sulfatides species subjected to collision-induced dissociation readily fragment to produce an intense ion at m/z 96.8 (HSO₄^-). The precisions of low and high concentration controls ranged from 5.4 to 19.9%. The sulfatides produced linear responses. Molecular species of sulfatides were barely detected in DBSs from normal individuals and the PD-OH group [mean (range), 0.07 (<0.05-0.34) and 0.13 (<0.05-0.22) μg/mL, respectively]. In contrast, the DBSs from MLD patients showed a marked increase in several molecular species of sulfatide [mean (range), 2.02 (1.18-3.89) μg/mL]. CONCLUSIONS Simultaneous detection for sulfatides using UPLC/MS/MS can be successfully applied to DBS analysis. This method provides a fast and effective screening and monitoring tool for the diagnosis and treatment of MLD.