Association of free vitamin D3 concentrations and asthma treatment failures in the VIDA Trial

John J. Lima, Mario Castro, Tonya King, Jason E. Lang, Victor E. Ortega, Stephen P. Peters, Loren C. Denlinger, Elliot Israel, Christine A. Sorkness, Michael E. Wechsler, Sally E. Wenzel, Lewis J. Smith

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5 Scopus citations


Background: Use of vitamin D3 serum concentrations as a biomarker of vitamin D status is questionable because of variation in vitamin D binding protein. Objective: 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. Methods: Free concentrations were directly measured by enzyme-linked immunosorbent assay and stratified into low, medium, and high groups: less than 5 pg/ mL (n = 65), 5 to 9 pg/ mL (n = 84), and greater than 9 pg/ mL (n = 48) after 12 weeks of supplementation with oral vitamin D3 and associated with outcomes. Results: 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. Conclusion: The use of free concentrations was inferior to total concentrations as a biomarker of efficacy of vitamin D3 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.

Original languageEnglish (US)
Pages (from-to)444-450.e1
JournalAnnals of Allergy, Asthma and Immunology
Issue number4
StatePublished - Oct 2018

All Science Journal Classification (ASJC) codes

  • Immunology and Allergy
  • Immunology
  • Pulmonary and Respiratory Medicine


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