In some respects the problems potentially limiting the utility of serum VDBP measurements mirror those that historically affected 25(OH)D assays.
on the basis of their study may also have broader implications for 25(OH)D measurements because of the integral role of VDBP in many automated assays.
The VDBP polymorphisms in exon 11 [Asp416Glu and Thr420Lys] were determined by polymerase chain reactions - restriction fragment length polymorphism (PCR-RFLP).
In VDBP Asp416Glu polymorphism, individuals homozygous for the Glu allele showed two bands (577 and 232 bp) while individuals homozygous for the Asp allele had a non-digested band at 809 bp (Figure 1A).
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The standardization of 25-OHD assays is slowly being addressed, but the elimination of matrix effects, of which VDBP is an example, will require the continual vigilance of analysts and clinicians and an ongoing dialogue with manufacturers.
2] Nonstandard abbreviations: 25-OHD, 25-hydroxyvitamin D; VDBP, vitamin D--binding protein; RMP, reference measurement procedure; SRM, Standard Reference Material; LC-MS/MS, liquid chromatography--tandem mass spectrometry; CPB, competitive protein-binding (method); DEQAS, Vitamin D External Quality Assessment Scheme; 24,25-[(OH).
To precipitate protein and dissociate vitamin D from VDBP, 150 [micro]L of sample, 150 [micro]L of 0.
This step released all 25OH-D from VDBP and eliminated important sources of interference, including heterophile antibodies, before incubation with the capture antibody.
In addition to this information, it is also imperative to realize that while some studies have proved that vitamin D2 is 30% to 50% less effective that vitamin D3 due to its less binding potential with VDBP
, (48), (49) others (50) show that vitamin D2 is as effective as vitamin D3 in maintaining and raising serum 25(OH) D concentrations.
We performed ESI-TOF MS for albumin, VDBP
, CRP, and apoAI using a column-free trap-and-elute approach (rather than traditional liquid chromatography gradient methods).
3], respectively; LC-MS/MS, liquid chromatography-tandem mass spectrometry; DEC, disposable extraction column; LLQ, lower limit of quantification; and VDBP
, vitamin D-binding protein.