Kim Hyun Jeong, Ji Misuk, Song Junghan, Moon Hee Won, Hur Mina, Yun Yeo Min
Department of Laboratory Medicine, Korean Association of Health Promotion, Seoul, Korea.
Department of Laboratory Medicine, Veterans Health Service Medical Center, Seoul, Korea.
Ann Lab Med. 2017 Jan;37(1):34-38. doi: 10.3343/alm.2017.37.1.34.
The associations of vitamin D deficiency with various clinical conditions highlighted the importance of vitamin D testing. Currently, clinicians measure only the total 25-hydroxyvitamin D [25(OH)D] concentration, regardless of its bioavailability. We aimed to determine the effect of vitamin D-binding protein (VDBP) on 25(OH)D bioavailability.
Serum samples were collected from 60 healthy controls, 50 pregnant women, and 50 patients in intensive care units (ICUs). Total 25(OH)D was quantified by liquid chromatography with tandem mass spectrometry, and VDBP levels were determined by using an ELISA kit (R&D Systems, USA). The bioavailable 25(OH)D levels were calculated by using total 25(OH)D, VDBP, and albumin concentrations.
In comparison with healthy controls, the total 25(OH)D concentration was significantly lower in ICU patients (median, 11.65 vs 18.25 ng/mL; P<0.00001), but no significant difference was noted between pregnant women (18.25 ng/mL) and healthy controls. The VDBP level was significantly lower in ICU patients (95.58 vs 167.18 μg/mL, P=0.0002) and higher in pregnant women (225.01 vs 167.18 μg/mL, P=0.008) compared with healthy controls. Nonetheless, the calculated bioavailable 25(OH)D levels of ICU patients and pregnant women were significantly lower than those of healthy controls (1.97 and 1.93 ng/mL vs 2.56 ng/mL; P=0.0073 and 0.0027).
A single marker of the total 25(OH)D level is not sufficient to accurately evaluate vitamin D status, especially in pregnant women. In cases where VDBP concentrations may be altered, VDBP measurements and bioavailable 25(OH)D calculations may help to determine vitamin D status accurately.
维生素D缺乏与多种临床病症的关联凸显了维生素D检测的重要性。目前，临床医生仅测量总25-羟维生素D[25(OH)D]浓度，而不考虑其生物利用度。我们旨在确定维生素D结合蛋白（VDBP）对25(OH)D生物利用度的影响。
收集了60名健康对照者、50名孕妇和50名重症监护病房（ICU）患者的血清样本。采用液相色谱串联质谱法定量总25(OH)D，并使用ELISA试剂盒（美国R&D Systems公司）测定VDBP水平。通过总25(OH)D、VDBP和白蛋白浓度计算生物可利用的25(OH)D水平。
与健康对照者相比，ICU患者的总25(OH)D浓度显著较低（中位数分别为11.65 ng/mL和18.25 ng/mL；P<0.00001），但孕妇（18.25 ng/mL）与健康对照者之间无显著差异。与健康对照者相比，ICU患者的VDBP水平显著较低（95.58 μg/mL对167.18 μg/mL，P=0.0002），而孕妇的VDBP水平较高（225.01 μg/mL对167.18 μg/mL，P=0.008）。尽管如此，ICU患者和孕妇计算得出的生物可利用25(OH)D水平显著低于健康对照者（分别为1.97 ng/mL和1.93 ng/mL对2.56 ng/mL；P=0.0073和0.0027）。
仅总25(OH)D水平这一单一指标不足以准确评估维生素D状态，尤其是在孕妇中。在VDBP浓度可能发生改变的情况下，测量VDBP并计算生物可利用的25(OH)D可能有助于准确确定维生素D状态。
