T-scores for bone mineral density (BMD) test.

Allogeneic hematopoietic stem cell transplant (aHSCT) patients are well known to be at high risk of vitamin D (vit D) deficiency. This study assessed whether a loading dose (100,000 IU) of vitamin D3 pre-aHSCT could effectively achieve and maintain sufficient post-transplant vit D levels (serum total 25 hydroxy vitamin D (25(OH)D) ≥ 75nmol/L). Dual-energy X-ray absorptiometry (DXA) was also conducted for bone health evaluation. 74 patients were enrolled and randomly assigned, in a 1:1 ratio, either to the high vit D group (single loading dose (100,000 IU) plus 2,000 IU vit D3 daily) or the control group (2,000 IU vit D3 daily). Vit D levels were measured at three time points (baseline, day 30 and day 100 post-aHSCT). At baseline, fewer than 50% patients had a sufficient 25(OH)D (control: 42.9%; high vit D: 43.6%). The proportion of patients with sufficient 25(OH)D (nmol/L) was increased at day 30 and day 100, with a trend of higher proportion in the high vit D group at day 30 (high vit D vs. control: 89.7% vs. 74.3%, p = 0.08). The increased 25(OH)D was significantly higher in the high vit D group at day 30 (high vit D vs. control: 29±25.2 vs. 14 ±21.9, p = 0.01). Insufficient vit D level before transplant (baseline) was an independent risk factor for vit D insufficiency (serum 25(OH)D < 75nmol/L) post-aHSCT (OR = 4.16, p = 0.03). DXA suggested significant bone loss for total hip in both groups, and in the femoral neck for the control group only. In conclusion, single loading dose vitamin D3 significantly increased total 25(OH)D levels at day 30 post-transplant, and the intervention was especially beneficial for patients with baseline vit D insufficiency. We acknowledge that the primary outcome at day 100 post-aHSCT indicating superiority of loading dose versus daily dose supplementation was not met.

众所周知，异基因造血干细胞移植（Allogeneic hematopoietic stem cell transplant, aHSCT）患者发生维生素D（vitamin D, vit D）缺乏的风险显著升高。本研究评估了异基因造血干细胞移植前给予100,000国际单位（IU）负荷剂量的维生素D3，能否有效实现并维持移植后充足的维生素D水平（血清总25-羟维生素D（25-hydroxy vitamin D, 25(OH)D）≥75纳摩尔每升，nmol/L）。同时采用双能X线吸收测定法（Dual-energy X-ray absorptiometry, DXA）对患者的骨骼健康状况进行评估。

本研究共纳入74例患者，以1:1的比例随机分为两组：高维生素D组（单次给予100,000 IU负荷剂量维生素D3，联合每日2,000 IU维生素D3维持治疗）与对照组（每日给予2,000 IU维生素D3维持治疗）。分别在三个时间点采集血样检测维生素D水平：异基因造血干细胞移植前基线期、移植后第30天及第100天。

基线期时，仅不足50%的患者血清25(OH)D水平充足（对照组为42.9%，高维生素D组为43.6%）。移植后第30天及第100天，血清25(OH)D水平充足的患者占比均较基线期升高；其中第30天时，高维生素D组的充足率呈现高于对照组的趋势（高维生素D组 vs 对照组：89.7% vs 74.3%，p=0.08）。

第30天时，高维生素D组患者的血清25(OH)D水平较基线的升高幅度显著高于对照组（高维生素D组 vs 对照组：29±25.2 vs 14±21.9，p=0.01）。移植前基线维生素D水平不足，是异基因造血干细胞移植后维生素D缺乏（血清25(OH)D<75nmol/L）的独立危险因素（优势比OR=4.16，p=0.03）。

双能X线吸收测定法检测结果显示：两组患者的全髋骨密度均出现显著丢失，对照组患者的股骨颈骨密度亦出现显著丢失。

综上，单次负荷剂量的维生素D3可显著提升移植后第30天的血清总25(OH)D水平，且该干预方案对基线维生素D不足的患者尤为有益。需说明的是，本研究未达到预先设定的主要研究终点：即异基因造血干细胞移植后第100天时，负荷剂量给药方案较每日维持给药方案更具优势。