Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase A (α-GAL A) deficiency. This enzyme contributes to the cellular recycling of glycosphingolipids such as galabiosylceramide (Ga), globotriaosylceramide (Gb), and globotriaosylsphingosine (lyso-Gb) by hydrolyzing the terminal α-galactosyl moiety. Urine and plasma α-GAL A substrates are currently analyzed as biomarkers for the detection, monitoring, and follow-up of Fabry disease patients. The sensitivity of the analysis of Ga is decreased by the co-analysis of its structural isomer, lactosylceramide (LacCer), which is not an α-GAL A substrate. A normal-phase ultraperformance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) methodology, allowing the baseline separation of 12 Ga isoforms/analogues from their lactosylceramide counterparts, was developed and validated in urine. The method was multiplexed with the analysis of 12 Gb isoforms/analogues having the same fatty acid moieties as those of Ga for comparison, and with creatinine for sample normalization. Urine samples were studied from 34 untreated and 33 Fabry males treated by enzyme replacement therapy (ERT) and 54 untreated and 19 ERT-treated Fabry females, along with 34 male and 25 female healthy controls. The chromatographic separation of Ga from LacCer increased the sensitivity of analysis, especially in women. One untreated Fabry female and two treated Fabry females presented abnormal levels of Ga but normal levels of Gb, supporting the importance of analyzing Ga in addition to Gb. Our results show that urine LacCer levels from females were significantly higher than those from males. Moreover, LacCer levels were not affected by Fabry disease for both males and females.

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Aim: Methylmalonic acid (MMA) analysis in urine represents a noninvasive approach to screening for vitamin B12 deficiency in older adults. A method allowing the analysis of MMA/creatinine in fasting urine collected on filter paper was developed/validated. Method: Dry urine specimens were eluted using a solution containing internal standards, filtrated and analyzed by ultra-performance LC-MS/MS. Results: The method allowed the chromatographic separation of MMA from succinic acid. Dried urine samples were stable for 86 days at room temperature. The MMA/creatinine ratios measured in urine collected on filter paper were highly correlated with values derived from the corresponding liquid specimens. Conclusion: This robust filter paper method might greatly improve the accessibility and cost–effectiveness of vitamin B12 deficiency screening in older adults.

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