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Abstract Details
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Activity Number:
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589
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Type:
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Contributed
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Date/Time:
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Wednesday, August 3, 2011 : 2:00 PM to 3:50 PM
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Sponsor:
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Biometrics Section
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| Abstract - #301308 |
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Title:
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Threshold Modeling in the Presence of Measurement Error: Application to Serum Vitamin D
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Author(s):
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Maria LaVonne Joseph*+ and Alicia Carriquiry and Wayne Fuller and Chris T. Sempos
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Companies:
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Iowa State University and Iowa State University and Iowa State University and National Institutes of Health
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Address:
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2219 Snedecor Hall, Ames, IA, 50011,
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Keywords:
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measurement error ;
segmented regression ;
parathyroid hormone
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Abstract:
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Vitamin D is essential to ensure bone hardness and strength. Consequently, insufficient levels of vitamin D can lead to fractures and osteoporosis. Those exhibiting vitamin D deficiency have been characterized by low levels of serum vitamin D (25(OH)D) and elevated levels of serum intact parathyroid hormone (iPTH). A function that has been suggested for the relationship between usual iPTH and usual 25(OH)D, where usual represents the long run average of the daily measurements of these quantities, is the segmented regression function. Simulation is used to assess the effects of measurement error on the estimates of the parameters of this function. An estimation procedure based on likelihood methodology is proposed and yields encouraging results in a simulation study.
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