Nemours Children's Health System, Jacksonville, Florida.
Washington University School of Medicine, St Louis, Missouri.
Ann Allergy Asthma Immunol. 2018 Oct;121(4):444-450.e1. doi: 10.1016/j.anai.2018.06.001. Epub 2018 Jun 14.
Use of vitamin D serum concentrations as a biomarker of vitamin D status is questionable because of variation in vitamin D binding protein.
To determine associations between free vitamin D3 concentrations and rates of treatment failure and exacerbations in patients with asthma participating in the Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness in Asthma (VIDA) trial.
Free concentrations were directly measured by enzyme-linked immunosorbent assay and stratified into low, medium, and high groups: less than 5pg/mL (n = 65), 5 to 9pg/mL (n = 84), and greater than 9pg/mL (n = 48) after 12 weeks of supplementation with oral vitamin D3 and associated with outcomes.
Outcomes did not associate with free concentrations: overall treatment failure rates were 0.60 (95% confidence interval [CI] 0.46-0.78), 0.53 (95%CI 0.40- 0.70), and 0.69 (95%CI 0.54-0.90)/person-year (P = .51), respectively; overall exacerbation rates were 0.28 (95%CI 0.17-0.48), 0.15 (95%CI 0.08-0.30) and 0.42 (95%CI 0.27-0.66)/person-year (P = .22). Mean (standard deviation) baseline free concentrations were lower in non-Hispanic blacks and Hispanics compared with non-Hispanic whites: 4.10 (1.33) and 4.38 (1.11) pg/mL vs 5.16 (1.65) pg/ml, (P < .001 and P = 0.038), respectively. Mean (standard deviation) baseline free concentrations differed between females and males: 4.57 (1.58) and 5.08 (1.41) (P = .026); and between non-overweight (body mass index [BMI] < 25) and overweight (BMI > 25): 5.45 (1.86) vs 4.54 (1.39) (P < .001). The free fraction differed by race and sex but not by BMI.
The use of free concentrations was inferior to total concentrations as a biomarker of efficacy of vitamin D supplementation in VIDA trial participants. Future studies of vitamin D status in patients with asthma should measure both free and total concentrations to better understand which marker of vitamin D function is most informative.
由于维生素 D 结合蛋白的差异，血清维生素 D 浓度作为维生素 D 状态的生物标志物的使用存在疑问。
确定游离维生素 D3 浓度与接受维生素 D 附加治疗增强哮喘患者皮质激素反应（VIDA）试验的哮喘患者治疗失败和加重率之间的关联。
通过酶联免疫吸附试验直接测量游离浓度，并分为低、中、高组：12 周口服维生素 D3 补充后，游离浓度分别小于 5pg/ml（n=65）、5-9pg/ml（n=84）和大于 9pg/ml（n=48），并与结局相关联。
结局与游离浓度无关：总体治疗失败率分别为 0.60（95%置信区间[CI]0.46-0.78）、0.53（95%CI 0.40-0.70）和 0.69（95%CI 0.54-0.90）/人年（P=0.51）；总体恶化率分别为 0.28（95%CI 0.17-0.48）、0.15（95%CI 0.08-0.30）和 0.42（95%CI 0.27-0.66）/人年（P=0.22）。与非西班牙裔白人和西班牙裔相比，非西班牙裔黑人和西班牙裔的基线游离浓度平均值（标准差）较低：分别为 4.10（1.33）和 4.38（1.11）pg/ml，而非西班牙裔白人的为 5.16（1.65）pg/ml（P<0.001 和 P=0.038）。女性和男性的基线游离浓度平均值（标准差）不同：4.57（1.58）和 5.08（1.41）（P=0.026）；非超重（体重指数[BMI] < 25）和超重（BMI > 25）的游离浓度平均值（标准差）不同：5.45（1.86）和 4.54（1.39）（P<0.001）。游离分数因种族和性别而异，但与 BMI 无关。
在 VIDA 试验参与者中，游离浓度作为维生素 D 补充疗效的生物标志物不如总浓度。未来对哮喘患者维生素 D 状态的研究应同时测量游离和总浓度，以更好地了解哪种维生素 D 功能标志物最具信息性。
