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BioMed Research International
Volume 2015, Article ID 168189, 9 pages
http://dx.doi.org/10.1155/2015/168189
Research Article

A Population-Based Model to Consider the Effect of Seasonal Variation on Serum 25(OH)D and Vitamin D Status

1Institute of Social and Preventive Medicine (IUMSP), University Hospital of Lausanne (CHUV), 1010 Lausanne, Switzerland
2Biomedicine, University Hospital of Lausanne, 1011 Lausanne, Switzerland
3Department of Genetic and Laboratory Medicine, Geneva University Hospitals, 1205 Geneva, Switzerland
4Unit of Population Epidemiology, Division of Primary Care Medicine, Department of Community Medicine, Primary Care and Emergency Medicine, Geneva University Hospitals, 1205 Geneva, Switzerland
5Department of Internal Medicine, Internal Medicine, University Hospital of Lausanne (CHUV), 1011 Lausanne, Switzerland
6Department for Ambulatory Care and Community Medicine, University of Lausanne, 1011 Lausanne, Switzerland
7Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA

Received 30 April 2015; Accepted 16 August 2015

Academic Editor: Sebastian Straube

Copyright © 2015 Philippe Vuistiner et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background. We elaborated a model that predicts the centiles of the 25(OH)D distribution taking into account seasonal variation. Methods. Data from two Swiss population-based studies were used to generate (CoLaus) and validate (Bus Santé) the model. Serum 25(OH)D was measured by ultra high pressure LC-MS/MS and immunoassay. Linear regression models on square-root transformed 25(OH)D values were used to predict centiles of the 25(OH)D distribution. Distribution functions of the observations from the replication set predicted with the model were inspected to assess replication. Results. Overall, 4,912 and 2,537 Caucasians were included in original and replication sets, respectively. Mean (SD) 25(OH)D, age, BMI, and % of men were 47.5 (22.1) nmol/L, 49.8 (8.5) years, 25.6 (4.1) kg/m2, and 49.3% in the original study. The best model included gender, BMI, and sin-cos functions of measurement day. Sex- and BMI-specific 25(OH)D centile curves as a function of measurement date were generated. The model estimates any centile of the 25(OH)D distribution for given values of sex, BMI, and date and the quantile corresponding to a 25(OH)D measurement. Conclusions. We generated and validated centile curves of 25(OH)D in the general adult Caucasian population. These curves can help rank vitamin D centile independently of when 25(OH)D is measured.