title: Quantitation of 25-OH-Vitamin-D₂ and 25-OH-Vitamin-D₃ in Urine Using LC-MS/MS.
abstract: Patients with significant proteinuria represent a unique population with respect to vitamin D status due to the urinary losses of vitamin D-binding protein (DBP) to which >99 % of circulating 25-hydroxy vitamin D (25(OH)D) is bound. Low serum concentrations of 25(OH)D have been found in children and adults with nephrotic syndrome (NS). However, previously described assays developed to quantify the magnitude of urinary loss are technically challenging. This chapter describes a simple and sensitive method to quantify 25(OH)D2 and 25(OH)D3 in urine specimens in a single analytical LC-MS/MS analysis. This assay is more sensitive than previously described radioimmunoassays and offers the ability to quantitate both forms of 25-hydroxy vitamin D. The assay involves no chemical derivitization, has a linear measurement range of 20-1500 pg/mL and displays imprecision (CVs) below 7 % at various concentrations across the analytical measurement range.
authors.affiliation: Department of Laboratory Medicine, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA. carlowd@mskcc.org.
authors.forename: Dean C
authors.initials: DC
authors.lastname: Carlow
authors.affiliation: Department of Laboratory Medicine, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Schofield
authors.affiliation: The Children's Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Denburg
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000652:urine*; D002112:Calcifediol / Q000652:urine*; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D057230:Limit of Detection; D053719:Tandem Mass Spectrometry / Q000379:methods*; D016482:Urinalysis / Q000379:methods*
chemical_list: D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol
keywords: 25-Hydroxy vitamin D2; 25-Hydroxy vitamin D3; Liquid chromatography; Mass spectrometry; Nephrotic syndrome; Urine