Masschrom 25 oh vitamin d3 d2 diagnostics kit

Serum 25(OH)D₂ and 25(OH)D₃ were analyzed by LC-MS/MS with an Agilent 1200 Infinity liquid chromatograph (Agilent Technologies, Waldbronn, Germany) coupled to a QTRAP® 5500 tandem mass spectrometer (AB SCIEX, Framingham MA, USA) using a MassChrom® 25-OH-Vitamin D₃/D₂ diagnostics kit (ChromSystems, Gräfelfing, Germany). The summation of serum 25(OH)D₂ and 25(OH)D₃ [total 25(OH)D] was used to reflect vitamin D status. Vitamin D deficiency was defined as having 25(OH)D levels of less than 50 nmol/L [20 ng/mL] [21 ]. The inter-assay and intra-assay coefficients of variation of total serum 25(OH)D level were 6.3% and 5.0%, respectively.

The serum levels of 25-OH-cholecalciferol (25OHD) were measured by certified commercial laboratories using liquid chromatography-mass spectrometry and the MassChrom® 25-OH-Vitamin D3/D2 diagnostics kit (ChromSystems, Munich, Germany). The intra-assay coefficient of variation (CV) was <5% and interassay CV was <6%. In accordance with previous guidelines for the definition of vitamin D status, calcifediol concentrations <50 nmol/L were defined as VDD [32 (link)]. Severe VDD was defined as concentration <25nmol/L. On 1 September 2016, the vitamin D analysis was switched from liquid chromatography-tandem mass spectrometry to a chemiluminescence immunoassay. In order to enhance homogeneity and to facilitate the interpretation, we included cases and controls with measured 25OHD up to 31 August 2016. If multiple values of vitamin D were found, the first value was taken, as this was closest to UAP.