Direct tandem mass spectrometric profiling of sulfatides in dry urinary samples for screening of metachromatic leukodystrophy

• Published in: Clinica chimica acta Vol. 425; pp. 153 - 159
• Main Authors: Kuchař, Ladislav, Asfaw, Befekadu, Poupětová, Helena, Honzíková, Jitka, Tureček, František, Ledvinová, Jana
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 21.10.2013
• Subjects: Adolescent; Case-Control Studies; Child; Child, Preschool; DEAE-Cellulose; DEAE-cellulose membrane; Desiccation; Dry urinary samples; Female; Humans; Infant; Isoforms; Leukodystrophy, Metachromatic - diagnosis; Leukodystrophy, Metachromatic - urine; Male; Membranes, Artificial; Middle Aged; Reference Standards; Screening for metachromatic leukodystrophy; Solid Phase Extraction; Specimen Handling - standards; Sulfoglycosphingolipids - urine; Tandem Mass Spectrometry; Urinary sulfatide; Tandem mass spectrometry; DUS; MLD; PTFE; IPN; Dry urinary samples; MS/MS; Psap-d; ASA; SRM; CV; S/N; Urinary sulfatide; Isoforms; DEAE; DEAE-cellulose membrane; Screening for metachromatic leukodystrophy; isoform profile number (ratio of the sum of the major five isoforms and the C18:0 sulfatide); arylsulfatase A; Diethylaminoethyl; dry urinary sample; metachromatic leukodystrophy; prosaposin deficiency; polytetrafluoroethylene; selected reaction monitoring; signal to noise ratio; coefficient of variation
• ISSN: 0009-8981; 1873-3492
• DOI: 10.1016/j.cca.2013.06.027

Prediagnostic steps in suspected metachromatic leukodystrophy (MLD) rely on clinical chemical methods other than enzyme assays. We report a new diagnostic method which evaluates changes in the spectrum of molecular types of sulfatides (3-O-sulfogalactosyl ceramides) in MLD urine. The procedure allows isolation of urinary sulfatides by solid-phase extraction on DEAE-cellulose membranes, transportation of a dry membrane followed by elution and tandem mass spectrometry (MS/MS) analysis in the clinical laboratory. Major sulfatide isoforms are normalized to the least variable component of the spectrum, which is the indigenous C18:0 isoform. This procedure does not require the use of specific internal standards and minimizes errors caused by sample preparation and measurement. Urinary sulfatides were analyzed in a set of 21 samples from patients affected by sulfatidosis. The combined abundance of the five most elevated isoforms, C22:0, C22:0-OH, C24:0, C24:1-OH, and C24:0-OH sulfatides, was found to give the greatest distinction between MLD-affected patients and a control group. The method avoids transportation of liquid urine samples and generates stable membrane-bound sulfatide samples that can be stored at ambient temperature. MS/MS sulfatide profiling targeted on the most MLD-representative isoforms is simple with robust results and is suitable for screening. •Easy transportation of urine samples dried on DEAE-cellulose membranes•Partial purification of sulfatides•Reliable monitoring of specific changes in the sulfatide isoforms in MLD patients•Use of the indigenous sulfatide isoform (with C18:0 fatty acid) as reference•Simplified analytical procedure and lower cost of analysis important for screening