Background The implementation of mass spectrometry to measure serum 25-hydroxyvitamin D [25(OH)D] concentrations has led to concerns regarding the measurement and reporting of the C3-epimer of 25-hydroxyvitamin D3 [3-epi-25(OH)D3], for which there is a near-total lack of data regarding its clinical significance. Methods We developed a chromatographic method to resolve (>90%) 3-epi-25(OH)D3 from 25(OH)D3 using a pentafluorophenyl propyl chromatographic column. Using LC-MS/MS, we determined the serum concentrations of 25(OH)D3 and 3-epi-25(OH)D3 in 626 patients aged 3 days to 94 y undergoing routine vitamin D testing. Results Comparison between DiaSorin RIA and the new LC-MS/MS method for total 25(OH)D had acceptable agreement. Our data indicate an increase in 25(OH)D3 rather than a reduction in epimer concentration. An average of 3.3 ng/ml of 3-epi-25(OH)D3 was detected in adolescents and adults. Inclusion of 3-epi-25(OH)D3 in the total 25(OH)D3 concentration resulted in 9% (< 1 y) and 3% (1 to 94 y) potential misclassification of patients as vitamin D sufficient. Conclusions The new LC-MS/MS method is capable of chromatographically separating 25(OH)D3 and 3-epi-25(OH)D3. It was used to confirm that the contribution of 3-epi-25OHD3 to total 25OHD3 concentrations decreases with age in infants and is detectable in adults.

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BACKGROUND: Newborn screening to identify infants with treatable congenital disorders is carried out worldwide. Recent tandem mass spectrometry (MS/ MS) applications have markedly expanded the ability to screen for Ͼ50 metabolic diseases with a single dried blood spot (DBS). The feature that makes metabolic disorders particularly amenable to screening is the presence of specific small-molecule metabolites. Many treatable disorders such as Wilson disease, however, are characterized by absent or diminished large proteins in plasma or within circulating blood cells, for which there are currently no cost-effective screening methods.

Therapeutic drug monitoring of tacrolimus and sirolimus plays a significant role in the clinical follow-up of transplant patients receiving IMS therapy. Success of transplant and favorable patient outcome relies on maintaining adequate therapeutic drug levels. The purpose of this research is to assess the clinical utility of remote collection of DBS for immunosuppressant monitoring and compare the IMS level in paired collections of venous whole blood and DBS. Sirolimus and tacrolimus levels were clinically correlated in capillary blood collected from a finger poke with venous whole blood from pediatric, post-transplant patients. The participants took the dried blood spot card home with them with a pre-addressed, postage-paid envelope and mailed it back to the laboratory. Overall, a small but statistically significant negative bias was observed (-0.6 ng/mL, p = 0.0011). A chart review was performed to assess whether clinical management would have changed, and none of the cases revealed a clinically significant change. Sirolimus in DBS also correlated with venous levels. Overall, a small but statistically negative bias was observed (-0.8 ng/mL, p = 0.029). In summary, analysis of IMS levels in DBS is possible, and the difference noted between capillary and venous blood is within the clinically acceptable limits.

The biosynthesis of the sphinganine analogue mycotoxins (SAMs) fumonisin B1 and the AAL toxins was studied by growing Fusarium moniliforme and Alternaria alternata f. sp. lycopersici in liquid culture. Radioactive and stable isotopically labeled amino acid, water, and molecular oxygen precursors were added to the culture media and toxins were analyzed using thin-layer chromatography, liquid scintillation counting, high-performance liquid chromatography (HPLC), 13C nuclear magnetic resonance (NMR) spectroscopy, and electrospray mass spectrometry (ESMS). Results indicated that glycine was incorporated directly into the AAL toxins and that methionine was incorporated into the AAL toxin methyl groups. Oxygens in tricarballylic acid moieties for fumonisin B1 and the AAL toxins were derived from H2O while the lipid backbone hydroxyls for fumonisin B1 and the AAL toxins originated from molecular oxygen. Isotopic enrichment patterns for the various AAL toxins showed marked differences among toxins, suggesting a complex, rather than sequential, biosynthetic pattern. Keywords: Mycotoxins; sphinganine analogue mycotoxins; isotope enrichment