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Vitamin D Status of Adults from Tropical Australia Determined Using Two Different Laboratory Assays: Implications for Public Health Messages

Authors

  • Madeleine Nowak,

    Corresponding author
    1. Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia
      Corresponding author email: madeleine.nowak@jcu.edu.au (Dr Madeleine Nowak)
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  • Simone L. Harrison,

    1. Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia
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  • Petra G. Buettner,

    1. Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia
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  • Michael Kimlin,

    1. Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia
    2. Australian Sun and Health Research Laboratory, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
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  • David Porter,

    1. Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia
    2. Pathology Queensland, Queensland Health, The Townsville Hospital, Townsville, Queensland, Australia
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  • Lee Kennedy,

    1. School of Medicine and Dentistry, James Cook University, Townsville, Queensland, Australia
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  • Rick Speare

    1. Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia
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Corresponding author email: madeleine.nowak@jcu.edu.au (Dr Madeleine Nowak)

Abstract

We measured serum 25 hydroxyvitamin D [25(OH)D] levels of ambulatory adults in tropical Australia to determine whether it is appropriate to continue promoting sun-safety in this population. In August 2006 (winter), self-administered questionnaires were completed by 145 Meals-on-Wheels volunteers (49.3% male; mean age 57.8 ± 14.7 years; 76.6% response) from Townsville, Queensland (Latitude 19oS). Serum 25(OH)D was analyzed using two common assays. Mean levels were 68.3 (SD ± 18.7; range 26–142) by DiaSorin Radioimmunoassay and 83.0 (SD ± 30.8; range 30–184) by DiaSorin Liaison® one. No participants were 25(OH)D deficient (<25 nmol L−1). Nine participants (6.2%) had 25(OH)D levels between 25 and 50 nmol L−1 (insufficient), by both methods (seven with a BMI ≥ 25). Twenty-eight participants (19.3%) had one result in the insufficient range and the other in the adequate range. Thus, almost all of these free-living adults in tropical Australia had adequate vitamin D levels at the end of winter. There was poor agreement between the two 25(OH)D assays. These results suggest it is appropriate to continue promoting sun-safe messages to the ambulatory Caucasian adult population of North Queensland, which has an extremely high incidence of skin cancer. The lack of agreement between the two assays is a concern. Few doctors are aware of this measurement issue.

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