About the Authors

Emma K. Larkin

Emma.Larkin@Vanderbilt.edu

Affiliation Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America

Tebeb Gebretsadik

Affiliation Department of Biostatistics, Vanderbilt University, Nashville, Tennessee, United States of America

Nathan Koestner

Affiliation Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America

Mark S. Newman

Affiliation ZRT Laboratory, Beaverton, Oregon, United States of America

Zhouwen Liu

Affiliation Department of Biostatistics, Vanderbilt University, Nashville, Tennessee, United States of America

Kecia N. Carroll

Affiliation Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, United States of America

Patricia Minton

Affiliation Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America

Kim Woodward

Affiliation Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America

Tina V. Hartert

Affiliation Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America

Competing Interests

Mark S. Newman is an employee of ZRT Laboratory, which sells Vitamin D testing. He conducted the vitamin D assay and prepared the protocol section of the manuscript, describing the LC/MS/MS method. The authors paid a fee to ZRT Laboratory for their service. ZRT Laboratory did not have any say in the data analysis or interpretation of the results. They did not have any input into the decision to publish. Mark Newman prepared the assay specifications. This does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: TVH. Performed the experiments: MSN. Analyzed the data: EKL TG. Wrote the paper: EKL MSN NK. Interpretation of data and critical review of manuscript: KNC PM KW. Data Manager: ZL.