Removal of 3-Epi-25-Hydroxyvitamin D3 Interference by Liquid Chromatography–Tandem Mass Spectrometry Is Not Required for the Measurement of 25-Hydroxyvitamin D3 in Patients Older than 2 Years

[摘要] To the Editor:There is growing evidence that 3-epi-25-hydroxyvitamin D3 (3-epi-25OHD3)1 is present in sera from most patients, not just sera from children younger than 1 year as was first described (1). Extended chromatography has been performed with liquid chromatography–tandem mass spectrometry (LC-MS/MS) assays (2–4) to eliminate interference from 3-epi-25OHD3, although one report (5) found that 3-epi-25OHD3 had a negligible effect on an LC-MS/MS assay (5). We examined the importance of separating the C3 epimer from 25-hydroxyvitamin D3 (25OHD3) in a large population of patients. We used both a proprietary LC-MS/MS method that does not resolve 3-epi-25OHD3 and an in-house epimer-resolving assay (epiRA) to measure 25OHD3 in excess serum samples from 71 infants <1 year old and 1046 adults. These samples were analyzed in 11 batches over a 2-month period.Samples were prepared by protein precipitation. Analytes were detected with atmospheric pressure chemical ionization (APCI) in the positive ion mode (AB Sciex) by monitoring m / z transitions of 383→257 and 389→263 for 25OHD3 and deuterated 25OHD3, respectively. Under the APCI conditions used, 3-epi-25OHD3 gave slightly different fragment yields and thus could not be quantified.The nonresolving assay (NRA) method consisted of online solid-phase extraction and analytical separation with the MassChrom® 25-OH-Vitamin D3/D2 Reagent kit (Chromsystems). The …

[学科分类] 过敏症与临床免疫学